Question 92·Medium·Text Structure and Purpose
Many paleobotanists have assumed that the spread of black walnut into northern valleys occurred slowly as seeds drifted along rivers and saplings crept up floodplains. However, sediment cores from lakes separated by hundreds of kilometers show black walnut pollen appearing abruptly in layers dated to the same few decades. Those dates align with archaeological evidence of a northward trade network. The researchers therefore argue that traders, not rivers, moved the nuts.
Which choice best describes the overall structure of the text?
For "overall structure" questions, first quickly paraphrase how the passage is built: identify what the opening does (introduce an idea, assumption, or situation), what the middle does (provide evidence, contrast, or examples), and what the ending does (conclude, propose, or predict). Use transition words like "however," "therefore," and "for example" as clues to shifts in function. Then, ignore the topic details and match your simple structure summary to the answer choice that best describes that pattern, eliminating any option that describes a different order (for example, a claim-first-then-evidence structure) or a different purpose (like staying undecided among multiple explanations).
Hints
Locate the main parts of the passage
Look at what the first sentence is doing, then what the middle sentences add, and finally what the last sentence concludes. Are they presenting one continuous story, or changing from one idea to another?
Use transition words as clues
Focus on the words "However" and "Therefore." What do they signal about how the later sentences relate to the first sentence?
Check each answer’s pattern against the passage
Ask yourself: Does the passage support the original explanation, present multiple possibilities without choosing, reverse the order (claim first, evidence after), or start with an old idea and replace it?
Paraphrase the structure in your own words first
Before looking at the answer choices, try to say in one sentence how the passage is organized from start to finish. Then pick the choice whose description best matches your paraphrase.
Step-by-step Explanation
Identify what the question is asking
The question asks for the overall structure of the text, not its topic or main idea. That means you need to describe how the author builds the argument from beginning to end (the pattern), not just what the author is talking about.
Summarize each part of the passage
Break the passage into logical chunks:
- First sentence: "Many paleobotanists have assumed that the spread of black walnut..." — This gives a common assumption about how black walnut spread (slowly via rivers and floodplains).
- Middle sentences: "However, sediment cores..." and "Those dates align..." — These introduce new evidence (pollen appearing abruptly in many places at the same time, matching a trade network timeline).
- Last sentence: "The researchers therefore argue that traders, not rivers, moved the nuts." — This is the researchers’ conclusion, offering a different explanation based on the new evidence.
Notice the key signal words
Pay attention to transition words:
- "However" signals a contrast with the earlier assumption, so the new information is challenging the old idea.
- "Therefore" signals a conclusion drawn from the evidence just described.
So the structure is: start with an existing explanation, bring in contrasting evidence, then draw a new conclusion from that evidence.
Match this pattern to the answer choices
The passage’s structure is: (1) an accepted explanation, (2) evidence that conflicts with it, and (3) a different explanation proposed from that evidence.
Therefore, the correct choice is: It presents a commonly held explanation, then introduces evidence that contradicts it and advances an alternative explanation.