ISEE Lower Level Quiz: Authors Purpose
20 questions · exam conditions
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Authors PurposeQuestion 1 of 20

The glow of a firefly on a warm summer evening is a magical sight, but it is not magic—it is chemistry. This phenomenon, known as bioluminescence, occurs when a chemical called luciferin mixes with an enzyme called luciferase, oxygen, and a special energy-carrying molecule. This reaction produces light without generating much heat, which is why fireflies are sometimes called "cold lights." The primary function of these flashes is communication. Each firefly species has its own unique flashing pattern, a sort of Morse code used to attract mates. A male will flash a specific sequence, and if a female of the same species is interested, she will flash back a particular response. This light is also a defense mechanism, as the firefly's blood contains a chemical that tastes bitter to predators. The bright flash serves as a warning: "I taste bad, don't eat me!"

The author's primary reason for mentioning that each species has a unique flashing pattern is to

suggest that it is difficult for scientists to study all the different firefly species.
prove that fireflies have one of the most advanced forms of animal communication.
emphasize the importance of light as a precise tool for firefly reproduction.
question whether different species of fireflies are able to understand each other.
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ISEE Lower Level Quiz

ISEE Lower Level Quiz: Authors Purpose

Practice Authors Purpose in ISEE Lower Level with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Authors Purpose, giving you a quick way to practice the rules, question types, and explanations that matter most for ISEE Lower Level.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

The glow of a firefly on a warm summer evening is a magical sight, but it is not magic—it is chemistry. This phenomenon, known as bioluminescence, occurs when a chemical called luciferin mixes with an enzyme called luciferase, oxygen, and a special energy-carrying molecule. This reaction produces light without generating much heat, which is why fireflies are sometimes called "cold lights." The primary function of these flashes is communication. Each firefly species has its own unique flashing pattern, a sort of Morse code used to attract mates. A male will flash a specific sequence, and if a female of the same species is interested, she will flash back a particular response. This light is also a defense mechanism, as the firefly's blood contains a chemical that tastes bitter to predators. The bright flash serves as a warning: "I taste bad, don't eat me!"

The author's primary reason for mentioning that each species has a unique flashing pattern is to

  1. suggest that it is difficult for scientists to study all the different firefly species.
  2. prove that fireflies have one of the most advanced forms of animal communication.
  3. emphasize the importance of light as a precise tool for firefly reproduction. (correct answer)
  4. question whether different species of fireflies are able to understand each other.
Explanation: The correct answer is C. Mentioning the unique patterns for each species highlights how specific and important the light signals are for attracting the correct mate, which is essential for reproduction. (A) is incorrect as the passage does not discuss the challenges scientists face. (B) makes a claim of being the "most advanced," which is an exaggeration not supported by the text. (D) is incorrect because the passage implies the unique patterns are to prevent other species from understanding, not to question if they can.

Question 2

The ancient art of origami transforms a flat sheet of paper into a three-dimensional sculpture through folding. The word itself comes from the Japanese words ori (folding) and kami (paper). While its exact origins are debated, origami became a popular art form in Japan during the Edo period (1603-1868). The core principle of traditional origami is that the sculpture should be created using only folds—no cutting, gluing, or marking the paper is allowed. This constraint is what makes origami both a challenge and a marvel. Artists must use a series of precise mountain folds (creases that point up) and valley folds (creases that point down) to create everything from simple boxes to intricate dragons. More than just a craft, origami is used by scientists and engineers to solve real-world problems, such as designing folded airbags for cars and collapsible telescopes for space missions.

Why does the author state that the "no cutting, gluing, or marking" rule makes origami "both a challenge and a marvel"?

  1. To suggest that these rules should be changed to make origami easier for beginners.
  2. To explain why origami is not considered a serious art form by many people.
  3. To highlight the skill required and the amazing results produced within these limits. (correct answer)
  4. To list all the essential supplies that are needed to start doing origami.
Explanation: The correct answer is C. By calling the constraint a "challenge," the author points to the difficulty and skill involved. By calling it a "marvel," the author emphasizes how impressive the final sculptures are, given the strict limitations. (A) is incorrect as the author presents the rule as a key feature, not something to be changed. (B) is an unsupported claim; the passage treats origami as a legitimate art and science. (D) is incorrect because the point is about what is not used, rather than what is needed.

Question 3

In 1930, India was under British rule, and the government imposed a heavy tax on salt, a mineral essential to everyone's diet. It was illegal for Indians to produce or sell their own salt; they were forced to buy it from the British. Mohandas Gandhi, a leader of the Indian independence movement, saw this unjust law as an opportunity for nonviolent protest. He organized a 240-mile march to the Arabian Sea, where he and his followers would make their own salt from the seawater. The Salt March, as it came to be known, began with just Gandhi and 78 followers but grew to include tens of thousands of people. When they reached the sea, Gandhi picked up a lump of salty mud and declared, "With this, I am shaking the foundations of the British Empire." This simple act inspired millions across India to defy the salt laws, leading to widespread civil disobedience that captured the world's attention and became a major turning point in the struggle for India's freedom.

This passage was most likely written to

  1. analyze the failures of the British Empire.
  2. instruct readers on how to organize a protest.
  3. inform readers about a key historical event. (correct answer)
  4. entertain readers with a story of adventure.
Explanation: The correct answer is C. The passage presents factual information about a specific historical event (the Salt March) in a clear, narrative style. Its purpose is to inform. (A) is too broad; the passage focuses on one event, not a full analysis of the British Empire's failures. (B) is incorrect because the passage describes a protest but does not provide instructions on how to organize one. (D) is incorrect because while the march was an adventure for its participants, the tone of the passage is historical and informative, not primarily entertaining.

Question 4

Read: Maya steps off the train in a new city. Tall buildings shine, and buses whoosh past her. She follows a street musician's song to a lively park. By sunset, she smiles, feeling brave and curious. Which of the following best describes the author's intent in this text?

  1. To explain the rules for riding a city bus
  2. To entertain readers with a child's city adventure (correct answer)
  3. To persuade readers to move to a big city
  4. To inform readers about every famous city park
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author tells a short, engaging story of Maya's adventure in a new city, focusing on her emotions and discoveries to create an enjoyable narrative. Choice B is correct because it accurately identifies the author's purpose of entertaining readers with a child's city adventure, as supported by the descriptive, story-like elements and positive resolution. Choice A is incorrect because it suggests the author aims to explain bus rules, which ignores the narrative style without instructional details. To help students: Teach them to identify key phrases and details that signal the author's intent, such as vivid descriptions indicating entertainment. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing storytelling with explanatory content.

Question 5

Read: A butterfly begins as an egg on a leaf. It becomes a caterpillar that eats leaves for energy. Next it forms a chrysalis, where its body changes. After about two weeks, an adult butterfly comes out and dries its wings. What is the author's main purpose in this passage?

  1. To entertain readers with a funny insect adventure
  2. To inform readers about the stages of a butterfly's life (correct answer)
  3. To explain only how long a chrysalis lasts
  4. To persuade readers to keep butterflies as pets
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author presents a step-by-step factual description of a butterfly's life cycle, from egg to adult, to educate readers on the process. Choice B is correct because it accurately identifies the author's purpose of informing readers about the stages of a butterfly's life, as supported by the sequential and factual details. Choice A is incorrect because it suggests the author aims to entertain with a funny adventure, which misinterprets the straightforward, educational tone without humorous elements. To help students: Teach them to identify key phrases and details that signal the author's intent, such as factual sequences indicating information. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing factual explanations with entertaining stories.

Question 6

Read: A caterpillar has tiny legs and a big appetite. It eats leaves and grows quickly. When it is ready, it forms a chrysalis to change. Later, it becomes a butterfly with wings. In what way does the author intend to engage the audience?

  1. By informing readers with facts about insect growth (correct answer)
  2. By discouraging readers from going outside near insects
  3. By telling a made-up mystery about a missing butterfly
  4. By focusing only on how to draw butterfly wings
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author describes the factual transformation of a caterpillar into a butterfly, highlighting key biological changes. Choice A is correct because it accurately identifies the author's purpose of informing readers with facts about insect growth, as evidenced by the objective, developmental details. Choice C is incorrect because it suggests the author aims to tell a made-up mystery about a missing butterfly, which does not align with the factual tone. To help students: Teach them to identify key phrases and details that signal the author's intent, such as biological facts indicating information. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing informative descriptions with fictional mysteries.

Question 7

Read: Leo visits a new city with his aunt. He gets lost near a bright market, but he stays calm. A kind baker points him toward the tall clock tower. When he reunites with his aunt, he feels proud. How does the author aim to affect the reader?

  1. To entertain readers with an exciting city moment (correct answer)
  2. To persuade readers to shop at that exact market
  3. To explain the history of clock towers in cities
  4. To focus only on the baker's job duties
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author narrates Leo's experience of getting lost and reuniting, using emotional details to create an engaging, positive story. Choice A is correct because it accurately identifies the author's purpose of entertaining readers with an exciting city moment, as supported by the narrative arc and resolution. Choice B is incorrect because it suggests the author aims to persuade readers to shop at that exact market, which ignores the story focus without promotional intent. To help students: Teach them to identify key phrases and details that signal the author's intent, such as emotional narratives indicating entertainment. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing storytelling with persuasive appeals.

Question 8

Read: A volcano erupts in steps. First, hot melted rock rises under the ground. Gas builds up and pushes the rock upward. Then pressure breaks the surface, and lava flows out. Ash and steam may rise into the sky. What is the primary goal of the author in writing this passage?

  1. To entertain readers with a scary mountain monster tale
  2. To explain how a volcano erupts, step by step (correct answer)
  3. To focus only on the color of hot lava
  4. To persuade readers to climb active volcanoes
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author outlines the sequential process of a volcanic eruption using factual steps to clarify how it occurs. Choice B is correct because it accurately identifies the author's purpose of explaining how a volcano erupts step by step, as evidenced by the structured, process-oriented description. Choice A is incorrect because it suggests the author aims to entertain with a scary mountain monster tale, which misaligns with the factual, non-fictional tone. To help students: Teach them to identify key phrases and details that signal the author's intent, such as step-by-step language indicating explanation. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing explanatory processes with fictional entertainment.

Question 9

Read: Recycling helps our town in simple ways. When we reuse paper, fewer trees are cut down. Cans and bottles can be melted and made into new items. If each family recycles weekly, our trash bins fill more slowly. Why did the author write this passage?

  1. To persuade readers that recycling is worth doing (correct answer)
  2. To explain everything about protecting the whole planet
  3. To entertain readers with a silly story about trash
  4. To describe only how to melt cans at home
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author highlights benefits of recycling and encourages families to participate, using examples like reusing paper and cans to build a case for action. Choice A is correct because it accurately identifies the author's purpose of persuading readers that recycling is worth doing, as evidenced by the motivational language and calls to action. Choice C is incorrect because it suggests the author aims to entertain with a silly story about trash, which overlooks the serious, advocacy-focused content. To help students: Teach them to identify key phrases and details that signal the author's intent, such as benefits and encouragements indicating persuasion. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing persuasive arguments with entertaining narratives.

Question 10

Read: The moon does not make its own light. It shines because it reflects sunlight. As it moves around Earth, we see different shapes called phases. A full moon happens when the moon's face is fully lit. What is the author's main purpose in this passage?

  1. To inform readers about why the moon looks different (correct answer)
  2. To persuade readers to stay up all night
  3. To entertain readers with a talking moon story
  4. To explain everything about space and all planets
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author provides factual information about why the moon appears in different phases, focusing on its reflection of sunlight and orbital movement. Choice A is correct because it accurately identifies the author's purpose of informing readers about why the moon looks different, as supported by the objective, educational details. Choice C is incorrect because it suggests the author aims to entertain with a talking moon story, which does not match the factual content without narrative elements. To help students: Teach them to identify key phrases and details that signal the author's intent, such as scientific facts indicating information. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing informative facts with fictional entertainment.

Question 11

Read: Our school should start a small garden behind the library. Students could grow tomatoes and herbs in raised beds. Working outside teaches teamwork and patience. We could even share extra vegetables with families. Why did the author write this passage?

  1. To persuade the school to create a student garden (correct answer)
  2. To inform readers about every plant in the world
  3. To entertain readers with a joke about tomatoes
  4. To describe only where the library is located
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author proposes starting a school garden and lists benefits like learning teamwork to encourage implementation. Choice A is correct because it accurately identifies the author's purpose of persuading the school to create a student garden, as shown by the suggestive language and positive outcomes. Choice C is incorrect because it suggests the author aims to entertain with a joke about tomatoes, which overlooks the advocacy without humor. To help students: Teach them to identify key phrases and details that signal the author's intent, such as proposals and benefits indicating persuasion. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing persuasive suggestions with humorous content.

Question 12

Read: Sofia explores a new city on foot. She smells warm bread from a corner café. Street signs help her find the museum with a blue roof. Inside, she whispers "wow" at a huge dinosaur skeleton. What is the primary goal of the author in writing this passage?

  1. To entertain readers with a child's city exploration (correct answer)
  2. To inform readers about all museums in every city
  3. To persuade readers to buy bread from that café
  4. To explain only how to read street signs
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author depicts Sofia's sensory experiences and discoveries in a new city through a short, engaging narrative. Choice A is correct because it accurately identifies the author's purpose of entertaining readers with a child's city exploration, as supported by the descriptive, story elements like smells and whispers. Choice B is incorrect because it suggests the author aims to inform about all museums in every city, which ignores the narrative without broad factual scope. To help students: Teach them to identify key phrases and details that signal the author's intent, such as sensory descriptions indicating entertainment. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing personal stories with comprehensive information.

Question 13

Read: Ella visits a new city and sees a huge bridge. She watches boats glide under it like quiet shadows. A friendly guide tells her the bridge is over 100 years old. Ella writes it in her notebook and keeps walking. What is the author's main purpose in this passage?

  1. To entertain readers with a calm city sightseeing scene (correct answer)
  2. To persuade readers to become professional tour guides
  3. To explain how to build a bridge step by step
  4. To inform readers about every bridge in the world
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author portrays Ella's calm observation of a bridge and interaction with a guide in a serene, narrative style. Choice A is correct because it accurately identifies the author's purpose of entertaining readers with a calm city sightseeing scene, as supported by the descriptive, relaxed storytelling. Choice C is incorrect because it suggests the author aims to explain how to build a bridge step by step, which lacks the instructional details present. To help students: Teach them to identify key phrases and details that signal the author's intent, such as observational narratives indicating entertainment. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing descriptive scenes with construction explanations.

Question 14

Read: Before a volcano erupts, magma rises toward the surface. Earthquakes may shake the ground as rock cracks. Gas escapes through small openings called vents. Finally, lava and ash may burst out from the top. Why did the author write this passage?

  1. To explain the warning signs and steps of an eruption (correct answer)
  2. To entertain readers with a volcano treasure hunt story
  3. To persuade readers to ignore earthquake warnings
  4. To focus only on what a vent looks like
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author describes the warning signs and progression of a volcanic eruption in a step-by-step manner to clarify the process. Choice A is correct because it accurately identifies the author's purpose of explaining the warning signs and steps of an eruption, as evidenced by the sequential indicators like earthquakes and gas. Choice B is incorrect because it suggests the author aims to entertain with a volcano treasure hunt story, which misfits the factual explanation. To help students: Teach them to identify key phrases and details that signal the author's intent, such as precursors and sequences indicating explanation. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing explanatory signs with adventure stories.

Question 15

Read: Our class should recycle paper every day. We use many worksheets, and the bin fills fast. If we recycle, we can turn old paper into new paper. It also keeps our classroom cleaner and more organized. How does the author aim to affect the reader?

  1. To persuade readers to recycle paper at school (correct answer)
  2. To inform readers about every type of classroom supply
  3. To entertain readers with a prank about worksheets
  4. To focus only on how fast one bin fills up
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author advocates for daily paper recycling in class, citing practical benefits to encourage adoption. Choice A is correct because it accurately identifies the author's purpose of persuading readers to recycle paper at school, as supported by the routine suggestions and positive outcomes. Choice C is incorrect because it suggests the author aims to entertain with a prank about worksheets, which overlooks the serious call to action. To help students: Teach them to identify key phrases and details that signal the author's intent, such as routines and benefits indicating persuasion. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing advocacy with humorous pranks.

Question 16

Read: A butterfly's wings must dry after it leaves the chrysalis. At first, the wings look small and wrinkled. The butterfly pumps fluid into them to make them strong. Soon it can fly to find food and mates. What is the primary goal of the author in writing this passage?

  1. To inform readers about what happens after a butterfly emerges (correct answer)
  2. To persuade readers to touch butterflies to help them
  3. To entertain readers with a butterfly race story
  4. To explain everything about all flying animals
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author details the post-emergence process for a butterfly, focusing on factual changes to its wings and abilities. Choice A is correct because it accurately identifies the author's purpose of informing readers about what happens after a butterfly emerges, as evidenced by the sequential, biological explanation. Choice C is incorrect because it suggests the author aims to entertain with a butterfly race story, which does not align with the informative content. To help students: Teach them to identify key phrases and details that signal the author's intent, such as processes indicating information. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing factual sequences with competitive stories.

Question 17

Read: Butterflies taste with their feet. When they land on a leaf, they can sense if it is good. Many butterflies drink nectar from flowers using a long tube. Their wings are covered with tiny scales that reflect color. Why did the author write this passage?

  1. To inform readers with interesting facts about butterflies (correct answer)
  2. To persuade readers to catch butterflies for collections
  3. To entertain readers with a butterfly superhero story
  4. To explain only how nectar tastes to butterflies
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author shares intriguing factual details about butterflies' senses and features to educate readers. Choice A is correct because it accurately identifies the author's purpose of informing readers with interesting facts about butterflies, as evidenced by the specific, biological trivia. Choice C is incorrect because it suggests the author aims to entertain with a butterfly superhero story, which does not match the factual presentation. To help students: Teach them to identify key phrases and details that signal the author's intent, such as unique facts indicating information. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing factual trivia with fictional tales.

Question 18

Read: Recycling is a habit that starts at home. Put paper in one bin and plastic in another. Rinse bottles so they do not smell. These small steps make recycling easier for everyone. In what way does the author intend to engage the audience?

  1. By persuading readers to recycle with simple, helpful steps (correct answer)
  2. By entertaining readers with a comedy about dirty bottles
  3. By focusing only on why bottles sometimes smell bad
  4. By describing every chore a family might do daily
Explanation: This question tests ISEE Lower Level reading comprehension skills, specifically identifying the author's purpose in a passage. Understanding the author's purpose involves recognizing the intent behind the text—whether to inform, entertain, persuade, or explain—and how it influences content presentation. In this passage, the author promotes recycling as a home habit by outlining easy steps and their benefits to encourage readers. Choice A is correct because it accurately identifies the author's purpose of persuading readers to recycle with simple, helpful steps, as supported by the practical instructions and positive framing. Choice B is incorrect because it suggests the author aims to entertain with a comedy about dirty bottles, which ignores the advisory tone. To help students: Teach them to identify key phrases and details that signal the author's intent, such as steps and habits indicating persuasion. Encourage practice with diverse texts to recognize different purposes. Watch for: students confusing helpful advice with comedic elements.

Question 19

The glow of a firefly on a warm summer evening is a magical sight, but it is not magic—it is chemistry. This phenomenon, known as bioluminescence, occurs when a chemical called luciferin mixes with an enzyme called luciferase, oxygen, and a special energy-carrying molecule. This reaction produces light without generating much heat, which is why fireflies are sometimes called "cold lights." The primary function of these flashes is communication. Each firefly species has its own unique flashing pattern, a sort of Morse code used to attract mates. A male will flash a specific sequence, and if a female of the same species is interested, she will flash back a particular response. This light is also a defense mechanism, as the firefly's blood contains a chemical that tastes bitter to predators. The bright flash serves as a warning: "I taste bad, don't eat me!"

The author discusses the firefly's bitter-tasting blood primarily to

  1. detail the complete chemical makeup of a firefly.
  2. illustrate another important function of the firefly's light. (correct answer)
  3. show that fireflies are more complex than other insects.
  4. give an example of a common predator that fireflies face.
Explanation: The correct answer is B. The passage connects the bitter blood to the light flash, explaining that the light serves as a warning sign about the bad taste. This shows that defense is another key function of the light. (A) is too broad; the passage only mentions one chemical in the blood, not the complete makeup. (C) is an unsupported comparison; the passage does not compare fireflies to other insects in terms of complexity. (D) is incorrect because the passage mentions predators in general but does not name a specific one.

Question 20

The glow of a firefly on a warm summer evening is a magical sight, but it is not magic—it is chemistry. This phenomenon, known as bioluminescence, occurs when a chemical called luciferin mixes with an enzyme called luciferase, oxygen, and a special energy-carrying molecule. This reaction produces light without generating much heat, which is why fireflies are sometimes called "cold lights." The primary function of these flashes is communication. Each firefly species has its own unique flashing pattern, a sort of Morse code used to attract mates. A male will flash a specific sequence, and if a female of the same species is interested, she will flash back a particular response. This light is also a defense mechanism, as the firefly's blood contains a chemical that tastes bitter to predators. The bright flash serves as a warning: "I taste bad, don't eat me!"

The author's main purpose in writing this passage is to

  1. describe the beautiful experience of watching fireflies at night.
  2. explain the scientific reasons behind a firefly's ability to glow. (correct answer)
  3. persuade readers to protect fireflies from their natural predators.
  4. compare the communication methods of fireflies to Morse code.
Explanation: The correct answer is B. The passage focuses on the chemical reaction (bioluminescence) and the functions of the light (communication and defense), which are all scientific explanations for the firefly's glow. (A) is incorrect because while the sight is called "magical," the passage's focus is on science, not the experience itself. (C) is incorrect because the passage explains the defense mechanism but does not make an argument for protecting fireflies. (D) is incorrect because the comparison to Morse code is a brief detail used to explain flash patterns, not the main purpose of the entire passage.