4th Grade ELA Quiz: Using Formal And Informal English Appropriately

What this quiz covers

This quiz focuses on Using Formal And Informal English Appropriately, giving you a quick way to practice the rules, question types, and explanations that matter most for 4th Grade ELA.

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.

Question 1

1. Yes; texting-style words are best when you want something quickly.
2. Yes; writing to the principal should sound casual like talking to friends.
3. No; he should use a polite greeting and complete sentences for the principal. (correct answer)
4. No; he should not ask for repairs at school at all.

Explanation: This question tests 4th grade speaking and listening skills: differentiating between contexts that call for formal English (e.g., presenting ideas) and situations where informal discourse is appropriate (e.g., small-group discussion), and using formal English when appropriate to task and situation (CCSS.SL.4.6). Formal English is used when presenting ideas, communicating with authority figures (like principals or teachers in official contexts), giving speeches, or writing formal letters and essays. Formal language uses complete sentences, no contractions ("do not" not "don't"), polite and respectful tone, proper titles (Mr., Mrs., Dr.), and more sophisticated vocabulary. Informal English is appropriate with friends and peers in casual conversation, small group discussions, brainstorming, texting family, or friendly contexts. Informal language uses contractions (it's, don't, can't), casual vocabulary (cool, awesome), conversational phrases, and a friendly tone. Both formal and informal English are correct—the key is matching your language to the audience, purpose, and situation. Amir writes a note to the principal saying "Hey, can u plz fix the swings?" to request playground repairs. The audience is the principal (an authority figure), and the purpose is making an official request for school maintenance. Amir uses informal features like casual greeting ("Hey"), text abbreviations ("u," "plz"), and casual tone, which don't match the formal context of communicating with school leadership about official matters. Choice C is correct because Amir should use a polite greeting (like "Dear Principal [Name]") and complete sentences (like "Could you please arrange for the swings to be repaired?") when writing to the principal, as this authority figure and official request context requires formal English to show respect and be taken seriously. Choice A is incorrect because texting-style abbreviations are never appropriate for formal communication with authority figures, regardless of urgency—formal requests can still be brief while using complete words and polite language. Students sometimes think abbreviations show efficiency or that informal language will make their request seem more urgent, but authority figures expect and deserve respectful, formal communication. Using inappropriate informal language with the principal could make Amir seem disrespectful or immature, potentially affecting how seriously his request is taken. To help students differentiate and use formal vs informal English appropriately: Teach the context test: Ask "Who is my audience? (Authority/unfamiliar or peers/friends?) What is my purpose? (Official/professional or casual/social?) What is the situation? (Presentation/writing or conversation/discussion?)"; create anchor chart with two columns: Formal English (presenting ideas, writing to principal, speeches, unfamiliar audiences) vs Informal English (small groups, friends, casual talk, familiar audiences); practice identifying contexts: Give scenarios and have students vote formal or informal; role-play: Have students practice same message in formal and informal ways; analyze examples: Show formal letter vs friendly note, presentation vs conversation. Watch for: students who think informal language makes them seem friendly or approachable to authority figures; students who use text speak in any written communication; students who don't understand that principals, even friendly ones, require formal communication for official matters; students who need explicit teaching about how informal language can undermine their message; practice rewriting informal requests formally.

Question 2

1. When writing the science report for the teacher to grade
2. When brainstorming story ideas with classmates in a small group (correct answer)
3. When giving a speech to the whole class at an assembly
4. When writing a letter to the principal about a school rule

Explanation: This question tests 4th grade speaking and listening skills: differentiating between contexts that call for formal English (e.g., presenting ideas) and situations where informal discourse is appropriate (e.g., small-group discussion), and using formal English when appropriate to task and situation (CCSS.SL.4.6). Formal English is used when presenting ideas, communicating with authority figures (like principals or teachers in official contexts), giving speeches, or writing formal letters and essays. Formal language uses complete sentences, no contractions ("do not" not "don't"), polite and respectful tone, proper titles (Mr., Mrs., Dr.), and more sophisticated vocabulary. Informal English is appropriate with friends and peers in casual conversation, small group discussions, brainstorming, texting family, or friendly contexts. Informal language uses contractions (it's, don't, can't), casual vocabulary (cool, awesome), conversational phrases, and a friendly tone. Both formal and informal English are correct—the key is matching your language to the audience, purpose, and situation. In the informal context of brainstorming story ideas with classmates in a small group, Carlos is communicating with peers for a casual, creative purpose, saying "What if the dog can talk? That would be hilarious!" which includes informal features like contractions ("would"), casual vocabulary ("hilarious"), and an excited, friendly tone. In the formal context of writing a short report for class, Carlos is communicating with the teacher for an official, graded purpose, using complete sentences, no contractions, and sophisticated vocabulary ("The experiment shows... The results were recorded"). Choice B is correct because brainstorming story ideas with classmates in a small group is appropriate for informal English since it's a casual discussion with peers for creative purposes, so Carlos can use contractions, speak casually, use conversational language, and be relaxed and friendly; using informal English in casual contexts helps build friendships and communicate naturally. Choice A is incorrect because it claims writing a science report for the teacher requires informal English, but submitting work for grading to an authority figure calls for formal English to show professionalism; students sometimes think informal English is fine in all classroom activities, but they need to consider the purpose (graded work vs casual brainstorming) and audience (teacher vs peers), as using formal English when needed demonstrates respect and seriousness. To help students differentiate and use formal vs informal English appropriately: Teach the context test by asking "Who is my audience? (Authority/unfamiliar or peers/friends?) What is my purpose? (Official/professional or casual/social?) What is the situation? (Presentation/writing or conversation/discussion?)"; create an anchor chart with two columns: Formal English (presenting ideas, writing to principal, speeches, unfamiliar audiences) vs Informal English (small groups, friends, casual talk, familiar audiences); practice identifying contexts by giving scenarios and having students vote formal or informal; role-play by having students practice the same message in formal and informal ways; analyze examples like a formal letter vs a friendly note. Watch for common pitfalls: students who think they must always use formal English in school (even with peers in discussion); students who think informal English is "bad" or "incorrect"; students who use inappropriately formal language with friends (sounds stiff and unfriendly); students who use inappropriately informal language with teachers or in presentations (seems disrespectful or unprepared); students who don't adjust their language at all regardless of context; also, students who confuse standard grammar with formal English (you can use standard grammar informally) or think slang is always wrong (it's fine in informal contexts).

Question 3

1. Using a polite greeting and closing, like "Dear Mr. Johnson" and "Sincerely" (correct answer)
2. Using short, playful comments to a buddy, like "Wanna trade snacks?"
3. Using excited, chatty phrases with a friend, like "I'm starving right now!"
4. Using quick texting shortcuts to a classmate, like "u" and "thx later"

Explanation: The correct answer is using a polite greeting and closing, like "Dear Mr. Johnson" and "Sincerely." These features are what make writing formal. A greeting that names the reader politely and a respectful closing show that Amir is writing carefully to a teacher for an official purpose. That is exactly what formal English does. The other answers all describe informal English, which fits talking with a friend, not applying for a job. Short, playful comments to a buddy, like "Wanna trade snacks?" use a casual contraction and a relaxed tone that would sound too friendly in an application. Excited, chatty phrases with a friend, like "I'm starving right now!" are cheerful and conversational, but not the polite, professional style a teacher expects. Quick texting shortcuts to a classmate, like "u" and "thx later" leave out full words and are fine in a text to a friend, but they look sloppy and disrespectful in a formal letter. Remember: to spot formal English, ask who the audience is and what the purpose is. Writing to a teacher for an official reason calls for polite, complete language, like a proper greeting and closing.

Question 4

1. Hey Ms. Perez! Thx so much for coming to talk to us. You were super cool and I learned a lot!
2. Dear Ms. Perez, Thank you for speaking to our class. I appreciated your visit. Sincerely, Sofia. (correct answer)
3. Ms. Perez, thanks a ton for stopping by our room today. It was really fun. See ya later, Sofia!
4. Hi Ms. Perez, you totally have to come back to see us again really soon because we all liked you!!!

Explanation: A thank-you email to a guest speaker is a formal situation. You are writing to an adult you do not know well, for an official purpose, so your language should show respect. The correct answer does this: it uses a proper greeting ("Dear Ms. Perez"), complete sentences, a polite tone ("Thank you," "I appreciated"), no contractions or slang, and a formal closing ("Sincerely, Sofia"). The choice beginning "Hey Ms. Perez! Thx" is too casual—it uses a shortcut spelling and slang like "super cool" that fit a friend, not a guest speaker. The choice ending "See ya later" also sounds friendly and relaxed ("thanks a ton," "See ya"), which does not match a formal message. The choice starting "Hi Ms. Perez, you totally have to come back" uses casual words ("totally," "have to") and extra exclamation points that feel like talking to a friend. All three would sound fine when whispering to a classmate like Riley, but for writing to an adult in an official way, the formal choice is the most appropriate. Remember: match your language to your audience and purpose. Informal English is not wrong—it just belongs in casual talk with friends, not in a formal thank-you email.

Question 5

1. Telling Jordan at lunch how awesome the exciting book she just finished was
2. Texting her mom to ask her for a ride home after practice ends
3. Writing a request letter to Principal Dr. Lee about buying more library books (correct answer)
4. Chatting with her friends about weekend plans while walking to the bus

Explanation: Formal English is used when you write or speak to someone in an official role, like a principal, for a serious purpose. Writing a request letter to Principal Dr. Lee about buying more library books is the situation that needs formal English: Maya is making an official request to a school leader, so she should use a polite tone, complete sentences, a proper title, and no slang or contractions. Telling Jordan at lunch how awesome the book was is a casual talk with a friend, so friendly, relaxed language fits best—this is informal. Texting her mom to ask for a ride home is a quick, familiar message to family, where informal English with contractions is natural and fine. Chatting with friends about weekend plans while walking to the bus is a social conversation with peers, which also calls for informal, everyday language. Remember: informal English is not "bad"—it is the right choice with friends and family. Only one situation here involves an authority figure and an official purpose, and that is the letter to the principal, so it is the one that requires formal English.

Question 6

1. Writing a quick note to her friend Chen about their plans for lunch that day
2. Sharing her ideas about a book with the whole class and her teacher during a graded talk (correct answer)
3. Talking with her close friends at recess about how their new playground game works
4. Sending a message to a family member at home to say that she is ready to be picked up

Explanation: Formal English is used when you present ideas to an audience, especially adults like a teacher, for an official purpose such as earning a grade. It uses complete sentences, no contractions, a polite tone, and careful word choices. Sharing your ideas about a book with the whole class and your teacher during a graded talk is exactly that kind of situation, so it calls for formal English like Yuki's sentence about courage. The other choices are all friendly, everyday situations where informal English fits better. Writing a quick note to your friend about lunch plans is casual, so relaxed words like "Hey" and "wanna" are fine. Talking with close friends at recess about a game is a chatty, social moment, not a formal one. Sending a message to a family member to say you are ready for pickup is a short, casual message to someone you know well. In each of these you are speaking with people you are comfortable with for a social or personal purpose, so formal English is not required. Only presenting to the class and teacher for a grade truly needs it.

Question 7

1. "That game was totally awesome and so much fun!"
2. "I cannot agree because the data shows a different result." (correct answer)
3. "Hey Chen, do you wanna go play a game outside?"
4. "Wow, that was really cool and super exciting to watch!"

Explanation: Formal English is the kind of language you use in serious situations, like giving a presentation to your class. It uses complete sentences, full words instead of contractions, and more grown-up vocabulary. The sentence "I cannot agree because the data shows a different result" is formal: it says "cannot" instead of "can't," it gives a clear reason, and it uses school words like "data" and "result." That fits presenting ideas to classmates. The sentence "That game was totally awesome and so much fun!" is friendly and excited, but words like "totally" and "awesome" are casual, so it is informal talk for a friend, not formal English. The sentence "Hey Chen, do you wanna go play a game outside?" starts with "Hey," uses the slang "wanna," and speaks to a buddy, so it is informal too. The sentence "Wow, that was really cool and super exciting to watch!" is enthusiastic, but "cool," "super," and "Wow" are casual words, so it is informal as well. Remember, being excited or using lots of words does not make language formal—formal English is about full words, complete sentences, and school-appropriate vocabulary for the situation.

Question 8

1. "Come on, let's go race down to the swings right now!"
2. "Hey, you'll totally be a rotten egg if you're last!"
3. "Our class would appreciate a new swing set for the playground." (correct answer)
4. "That swing set would be so awesome and super fun for us!"

Explanation: The phrase "Our class would appreciate a new swing set for the playground" shows formal English. It uses a polite, respectful tone, a complete sentence with no contractions, and grown-up vocabulary like "appreciate." This is the right way to write to the principal, who is an authority figure. The other three phrases all sound friendly and casual, like something you would say to a buddy at recess. "Come on, let's go race down to the swings right now!" is excited and uses the contraction "let's," so it fits playtime with a friend, not a letter. "Hey, you'll totally be a rotten egg if you're last!" uses the slang "totally" and a teasing joke, which is fun with friends but too casual for the principal. "That swing set would be so awesome and super fun for us!" uses casual words like "awesome" and "super fun," which sound informal even though the idea is polite. Remember: formal English matches an official audience and purpose, while informal English fits chatting with friends.

Question 9

1. When writing a letter to thank the school principal for her help
2. When chatting with her classmates during a small group discussion (correct answer)
3. When leaving a message on the school office answering machine
4. When giving a spoken report to her whole fourth-grade class

Explanation: Informal English is the casual, friendly language you use with friends and peers when the situation is relaxed. Chatting with classmates during a small group discussion is exactly that kind of setting—it is a comfortable, cooperative time when everyday conversational language helps everyone share ideas easily. That is why this is the best answer. Writing a letter to thank the school principal calls for formal English, because you are showing respect to an adult in charge with polite, complete sentences. Leaving a message on the school office answering machine also needs formal English, since you are speaking to staff you do not know well and should sound clear and polite. Giving a spoken report to your whole class is a formal moment too, where you present your ideas carefully and use your best language. The trick is to notice that three of these situations involve an audience or a task that expects your formal, respectful voice, while only relaxed talk with peers invites your informal, everyday voice.

Question 10

1. Texting her friend Jamal to ask if he wants to meet at the park after school
2. Writing a letter to the school principal to request more books for the library (correct answer)
3. Sharing her ideas out loud during a small group discussion with her classmates
4. Chatting with her friends about their favorite video games during lunchtime

Explanation: The situation that requires formal English is writing a letter to the school principal to request more books. When you write to a principal, your audience is an authority figure and your purpose is an official request, so you should use polite language, complete sentences, and a respectful greeting. This shows you are serious and considerate. Texting a friend to ask about meeting at the park is casual and social, so informal language like short, friendly words fits perfectly between peers. Sharing ideas in a small group discussion with classmates is a collaborative, conversational moment, so friendly language is natural and appropriate there too. Chatting with friends about video games at lunch is a relaxed, social conversation, so informal English is exactly what belongs. Remember: it is not the school location that decides the register—it is your audience and purpose. Even at school, talking with friends and classmates usually calls for informal English, while writing to a principal for an official reason calls for formal English.

Question 11

1. Chatting with his friend Amir at recess about which trading cards they want to swap
2. Welcoming a guest speaker in front of the whole school at the morning assembly (correct answer)
3. Sharing silly story ideas with his writing partner while they plan a class project
4. Sitting with his buddies at the lunch table and joking around about the weekend

Explanation: Formal English means using polite words, complete sentences, and no slang. You use it when you speak to a large or important audience, like at a public event. Welcoming a guest speaker in front of the whole school is the right answer because Chen is representing his school to an important visitor and a big, mixed audience of students and teachers. That calls for a respectful greeting and formal words. Chatting with Amir about trading cards at recess is a relaxed talk between two friends, so casual language fits fine there. Sharing silly story ideas with a writing partner is a friendly small-group moment where informal talk helps ideas flow. Sitting with buddies at the lunch table joking around is a social time with friends, so casual language belongs there too. Remember, formal isn't 'better' than informal—each one fits a different situation. Only speaking to the whole school at assembly needs formal English.

Question 12

1. "Today I will explain my results, and I cannot wait to answer your questions."
2. "u coming to soccer? it's gonna be fun." (correct answer)
3. "Good afternoon, class. I am pleased to share what I discovered."
4. "Thank you for listening. I would appreciate any helpful feedback."

Explanation: The right answer is "u coming to soccer? it's gonna be fun." This message uses informal English, which is perfect for texting a friend. You can spot the informal features: the texting shortcut "u" instead of "you," the contraction "it's," the casual word "gonna" instead of "going to," and the friendly, relaxed tone. The other choices are all formal English, which fits a presentation but not a casual text. "Today I will explain my results, and I cannot wait to answer your questions" uses complete sentences and the full form "cannot" instead of "can't." "Good afternoon, class. I am pleased to share what I discovered" uses a polite greeting and no shortcuts. "Thank you for listening. I would appreciate any helpful feedback" uses polite, careful wording like "I would appreciate." None of these use texting shortcuts, contractions, or slang, so they are formal, not informal. Remember, formal English isn't "better" than informal English. The smart move is matching your language to who you are talking to. You would use formal English for a class presentation and informal English for a quick text to a buddy.

Question 13

1. Use polite, complete sentences at the assembly; use casual, friendly words with Yuki (correct answer)
2. Use casual, friendly words at the assembly; use polite, complete sentences with Yuki
3. Use polite, complete sentences in both places so she treats everyone equally
4. Use casual, friendly words in both places so she always sounds relaxed

Explanation: Emma should match her language to who she is talking to and why. At the assembly, she is speaking to a large audience and introducing a guest, so polite, complete sentences fit that formal moment. With Yuki, she is chatting with a friend, so casual, friendly words fit that relaxed moment. That is why choosing polite sentences for the assembly and casual words for Yuki is the best answer. The choice that flips this—casual words at the assembly and formal sentences with a friend—matches the wrong language to each situation, which would sound too silly on stage and too stiff in a text. Using polite, complete sentences in both places treats everyone equally, but sounding that formal in a quick text to a friend is not necessary or natural. Using casual, friendly words everywhere might feel relaxed, but slang like "OMG" and "lol" is not respectful enough when introducing a speaker to a crowd. Good communicators switch their language to fit the audience and purpose.

Question 14

1. "Hi Mr. Patel, I was wondering if you could meet with me after school sometime this week?"
2. "Dear Mr. Patel, would it be possible to meet with me after school this week to get some help?" (correct answer)
3. "Hey Mr. Patel, just checking if we can meet up after school to go over some stuff soon."
4. "Yo Mr. Patel, can u meet me after school this week? Thx, I really need the help!"

Explanation: An email to a teacher is a formal situation, so Sofia should use polite, respectful language and complete sentences. The best choice opens with a proper greeting ("Dear Mr. Patel"), makes a courteous request ("would it be possible"), and keeps a respectful tone the whole way through. That matches writing to an authority figure. The option starting with "Hi Mr. Patel" is close, but "Hi" and "wondering" are more casual than a teacher email calls for, so it is not the strongest formal choice. The one starting with "Hey Mr. Patel" sounds too relaxed, using "Hey," "meet up," and "stuff"—friendly words better suited for a text to Maya. The choice beginning with "Yo Mr. Patel" is the most casual of all, mixing slang ("Yo") with texting shortcuts ("u," "Thx"), which is fine for friends but disrespectful in a message to a teacher. Remember to ask yourself: Who is my audience, and what is my purpose? Writing to a teacher calls for formal English, even in an email.

Question 15

1. "I am responsible and I will always arrive right on time."
2. "I'm gonna be late lol." (correct answer)
3. "I will complete every single one of my tasks carefully."
4. "I truly cannot afford to miss my shift tomorrow."

Explanation: The sentence "I'm gonna be late lol" is informal English. It uses the contraction "I'm," the casual word "gonna" instead of "going to," and the text shortcut "lol." These friendly, relaxed features fit a text message to a friend like Keisha. The other choices are all formal English, so they do not answer the question. "I am responsible and I will always arrive right on time" uses full words with no contractions and a serious tone that fits a job application. "I will complete every single one of my tasks carefully" is also polite and formal, with complete sentences and no slang. "I truly cannot afford to miss my shift tomorrow" spells out "cannot" and sounds respectful and formal, not casual. Remember: informal English uses contractions, casual words, and text shortcuts for friends, while formal English uses complete, polite sentences for official writing. Only the text to Keisha shows Carlos using informal language, so it is the best answer.

Question 16

1. Writing a quick friendly note to Riley all about a funny movie
2. Talking with your close friends at lunch about your fun weekend plans
3. Presenting your ideas to classmates and your teacher during a school project (correct answer)
4. Messaging a parent at home to ask what time they can pick you up

Explanation: The right answer is presenting your ideas to classmates and your teacher during a school project. When you present ideas in school, your audience includes your teacher and your purpose is serious and academic, so you need formal English with complete sentences and no slang. That is why Keisha says "It is my opinion" in her report instead of casual words. Writing a friendly note to Riley about a movie is casual sharing between friends, so informal words like "Hey!" and "cool" fit perfectly. Talking with your friends at lunch about weekend plans is also a relaxed, social chat where informal language sounds natural. Messaging a parent to ask about pickup time is a quick, comfortable message to family, so friendly informal words are fine there too. All three of those are casual situations with people you know well. Only presenting to classmates and a teacher during a school project is an official moment that calls for formal English.

Question 17

1. Use more polite, complete sentences in the presentation than in chatting. (correct answer)
2. Use more casual words and contractions in the presentation than in chatting.
3. Use the same relaxed, everyday language in both the presentation and the chat.
4. Use the most formal, careful language when chatting with a classmate like Carlos.

Explanation: When you speak to different people, you match your language to the situation. A science presentation is a formal moment in front of the whole class, so Yuki should use polite, complete sentences and full words like "I will." This is why using more polite, complete sentences in the presentation than in chatting is the best answer. Using more casual words and contractions in the presentation gets it backward—casual talk fits chatting with a friend, not a formal presentation. Using the same relaxed, everyday language in both situations ignores that a presentation calls for a more formal tone than a friendly chat. Using the most formal, careful language when chatting with Carlos also mixes things up, since a relaxed conversation with a classmate does not need that level of formality. Yuki shows strong communication skills by speaking formally when presenting and casually when talking with a friend.

Question 18

1. It is too formal for talking with a friend during recess. (correct answer)
2. It is too formal for a school report but just right for chatting with a friend.
3. It is missing polite words that Yuki expects to hear from a good friend.
4. It is fine because using fancy words is the friendly way to invite a buddy.

Explanation: Marcus is just asking a friend to play at recess, which is a casual, friendly moment. The best choice explains that his words are too formal for talking with a friend during recess. Saying "I would be most appreciative if you would join me" sounds stiff, like a speech, when a relaxed "Wanna play kickball?" fits chatting with a buddy. That mismatch is why Yuki laughs. The idea that his words are too formal for a report but perfect for a friend is backwards—formal language suits a report, not a playground invitation. The idea that he is missing polite words is wrong too; his sentence is already extra polite, so the problem is too much formality, not too little. The idea that fancy words are the friendly way to invite a buddy is also incorrect, because overly formal language with friends sounds distant instead of warm. Good speakers match their words to the situation: friendly and casual with friends, formal for reports, speeches, or writing to a principal. Here, casual language is the right fit.

Question 19

1. It is too informal for an authority figure and an official request (correct answer)
2. It is too formal for a friendly conversation with a group of classmates
3. It uses a title, so it is polite enough for an official request
4. It is casual, but casual language always works for any audience

Explanation: When you write to a principal to ask for something official, you are talking to an authority figure and making a real request, so your language should be respectful and formal. Chen's note is too informal for this: it uses a casual greeting ("Hey Mr. K"), texting shortcuts ("u," "plz," "thx"), and no polite structure. That is why the best answer is that it is too informal for an authority figure and an official request. The answer saying it is too formal for a friendly conversation with classmates is wrong because the note goes to the principal, not classmates, and it is actually too casual, not too formal. The answer saying the title makes it polite enough is wrong because writing "Mr." does not fix the shortcuts and casual tone around it. The answer saying casual language always works for any audience is wrong because the audience and purpose decide how formal you should be; casual language fits friends, but an official request needs formal language. Remember, formal English is not "better" than informal English—you just match your language to who you are talking to and why.

Question 20

1. Yes, it is polite and uses complete sentences for a teacher audience (correct answer)
2. No, it is too casual because it asks the teacher a direct question
3. No, it needs friendly slang like "hey" to sound relaxed for a teacher
4. Yes, but only because short emails are the fastest way to reach a teacher

Explanation: Keisha's email is appropriate because it is polite and uses complete sentences for a teacher audience. She writes a proper greeting, uses "please" and "Thank you," and avoids slang, which shows respect when writing to a teacher for an official reason. The choice saying it is too casual because it asks a direct question is wrong: a question can be perfectly formal when it is worded politely, like "Could you please tell me what I missed?" Asking is not the same as being casual. The choice saying it needs friendly slang is wrong because slang like "hey" fits talking to a friend such as Jordan, not writing to a teacher. Formal writing avoids slang. The choice saying it works only because short emails are fastest is wrong because speed is not the reason the language fits. The email is appropriate because its polite, complete-sentence style matches a teacher audience, not because it is quick to send.