This is a transitions question. Choice D (Finally) is correct—signals the last item in a sequence. The paragraph lists four sleep stages (three NREM, then REM), and "Finally, the fourth stage" appropriately introduces the last one. Choice A (Conversely) emphasizes contrast, which works but doesn't signal sequence as clearly. Choice B (Therefore) suggests causation. Choice C (For example) suggests illustration. Pro tip: For numbered sequences, "Finally" or "Lastly" work well for the final item.

This is a sentence placement question. Choice D (After Sentence 4) is correct—Sentence 4 describes "flushing out toxic proteins," and the new sentence about "Without this nightly wash cycle" refers back to that flushing process. The metaphor elaborates on what happens without the clearance system. Choices A, B, C place it before the flushing mechanism is described. Pro tip: Place sentences after the content they refer to or elaborate upon.

This is a paragraph selection question. Choice C (Paragraph 3) is correct—Paragraph 3 is where the glymphatic system is introduced and explained ("In 2013, researchers discovered the 'glymphatic system'..."). Attribution to Dr. Nedergaard would logically go in the same paragraph where the discovery is discussed. Choices A, B, D are paragraphs that don't discuss the glymphatic system. Pro tip: Place specific details in the paragraph that discusses that topic.

This is a transitions/conjunctions question testing logical relationships within a sentence. Choice A (NO CHANGE: while) is correct—"while" sets up the contrast between native plants (survive fire) and invasive weeds (are destroyed). It signals simultaneous but opposing outcomes. Choice B (so) suggests causation, implying invasives die because natives survive, which isn't the relationship. Choice C (therefore) also suggests causation incorrectly. Choice D (and) suggests simple addition without capturing the contrast. Pro tip: "While" effectively signals contrast within sentences.

This is a transitions question. Choice C (Therefore) is correct—signals logical consequence. The previous sentence states "diversity is key" (premise), and this sentence explains the action required: "therefore, restorationists must harvest seeds" (consequence). The seed collection is the method to achieve diversity. Choice A (For example) incorrectly suggests harvesting seeds is an example of diversity rather than the method to achieve it. Choice B (However) signals contrast that doesn't exist. Choice D (Nevertheless) signals concession, which doesn't fit. Pro tip: "Therefore" connects premises to their logical conclusions or required actions.

The correct answer is A (NO CHANGE — Furthermore). This question tests whether the transition word correctly signals the logical relationship between two sentences. The preceding sentence describes one remarkable capability of the mycorrhizal network: trees sending chemical warning signals to alert neighbors under attack. The sentence that follows describes another remarkable capability: hub trees channeling carbon and nitrogen to struggling seedlings. These are two separate examples of the same phenomenon — the network's ability to share information and resources. 'Furthermore' correctly signals addition: 'here is another thing this network does.' G ('However') signals contrast — but there is no contrast here; both sentences describe positive capabilities of the same system. H ('Alternatively') implies a choice between two options, which is not the relationship here. J ('For example') would imply the second sentence is a specific illustration of the first, but these are two distinct capabilities, not a general statement followed by an example. Pro tip: on transition questions, identify the logical relationship first — addition, contrast, cause-effect, or example — then find the transition word that matches.

The correct answer is D. This is a LEAST acceptable question — three transitions work logically and one fails. The context: Paragraph 4 established that these networks are fragile and that logging destroys them. Paragraph 5 then states that ecologists are urging forestry departments to change their practices. This is a clear cause-and-effect relationship: because the networks are being destroyed, ecologists are calling for change. A ('Consequently'), B ('As a result'), and C ('For this reason') all correctly signal cause-and-effect — they are functionally equivalent here and all acceptable. D ('On the other hand') signals contrast or opposition — as if the ecologists' response is somehow in tension with or contrary to what was just stated. But the ecologists' advocacy is a direct response to the problem described, not a contrasting viewpoint. Using 'On the other hand' would imply the passage is presenting two sides of a debate, when it is presenting a problem and its logical consequence. On LEAST acceptable questions, the wrong answer almost always fails because it signals the wrong logical relationship.

The correct answer is B. The preceding sentence explains that the laser removes filth without heating or damaging the artwork. The following sentence states that the painting can then reveal its true colors. This is a cause-and-effect relationship: because the laser safely removes the grime, the original colors are revealed. "As a result" correctly signals this causal connection. A ("On the other hand") signals contrast — but there is no contrast here; the revealed colors are a direct consequence of the successful laser removal. C ("However") also signals contrast incorrectly. D ("Similarly") implies a parallel example is being introduced, which is not the case. Pro tip: Before choosing a transition, label the relationship: is the second idea a contrast, a result, an addition, or an example? Here, the cause is the laser's action and the result is the revealed colors — cause-and-effect demands "as a result" or equivalent.

This question tests whether adding a sentence maintains paragraph focus and unity. The paragraph discusses effective interview questions, specifically those that prompt storytelling rather than yes/no answers. The proposed addition about weather small talk introduces a completely different type of interview opener that doesn't relate to the paragraph's focus on story-prompting questions. Choice C correctly identifies that this sentence shifts away from the main topic (effective interview questions) toward unrelated conversation topics. The addition doesn't provide an example of the recommended approach or serve as a useful contrast—it simply introduces irrelevant information. For add/delete questions, ensure new sentences directly support or enhance the paragraph's central argument rather than introducing tangential topics.

This question tests the ability to evaluate whether an added sentence enhances unity and cohesion by maintaining relevance to the paragraph's focus. The paragraph narrates a chronological sequence of the writer's bike repair process, starting with acquiring the bike, preparing tools, and encountering mechanical challenges with logical resolutions. The correct choice, C, indicates that the sentence should not be added because it introduces irrelevant details about lighting conditions that divert attention from the core repair steps and mechanical issues. Choices A and B are distractors as they misinterpret the sentence as providing essential explanation or setting, but the struggle with the chain stems from tension, not visibility, and the setting is already established. Choice A incorrectly suggests repetition, whereas the sentence introduces new but off-topic information. In add/delete questions, focus on whether the sentence maintains the paragraph's focus and advances the logical flow without introducing distractions.