Question 153·Hard·Text Structure and Purpose
Analyzing thousands of hours of underwater acoustic recordings collected across two migration seasons near a heavily trafficked shipping lane, marine ecologist Lina Tran documented that humpback whales systematically inserted longer silent intervals between song phrases during periods of intense vessel activity, then returned to a standard cadence when ambient noise subsided. Tran argues that this temporal adjustment minimizes acoustic masking while preserving the recognizable structure of the songs.
Which choice best states the main purpose of the text?
For “main purpose” questions, first summarize the passage in your own words in one short sentence, focusing on what the author is doing (reporting a study, telling a story, arguing for a policy, etc.). Then scan the answer choices and underline the key verb and any extra details in each (like “argue,” “criticize,” “summarize,” “policy,” “unexpected”). Eliminate any choice whose verb does not match the passage’s tone and structure, or that introduces ideas (such as policy recommendations, strong criticism, or surprises) that are never mentioned. The remaining choice that best matches your one-sentence summary is usually correct.
Hints
Look at the overall task of the passage
Ask yourself: Is the author mostly telling you about what someone did and found, or are they mainly trying to convince you of a policy, criticize others, or describe a big surprise?
Notice key details about the research
Pay attention to the description of the recordings, the shipping lane, the changes in silent intervals and cadence, and the explanation Tran gives—what do these details show the passage is focused on?
Use the verbs in the choices
Underline the main verbs in each answer choice (for example, "describe," "present an analysis critiquing," "summarize," "argue"). Which verb best fits what the passage actually does, and which choices add purposes or topics (like policies or criticism) that never appear?
Step-by-step Explanation
Identify what the passage is mainly doing
Read the passage and ask: Is it telling a story, making an argument for a policy, criticizing methods, or reporting research findings?
Here, the passage:
- Names a researcher (marine ecologist Lina Tran).
- Describes what she did (analyzed thousands of hours of recordings across two migration seasons near a busy shipping lane).
- States what she documented (whales inserted longer silent intervals during intense vessel activity and went back to standard cadence when noise decreased).
- Gives her interpretation (this adjustment reduces masking while keeping song structure recognizable).
That pattern is typical of a short summary of a study and its main conclusion.
Focus on topic and scope
Next, define the specific subject of the study: it is about how shipping noise affects the timing (silent intervals, cadence) of humpback whale songs.
There is no mention of:
- Policy proposals or regulations.
- A major surprise that forces scientists to rethink what song cadence usually means.
- A critique of other researchers' methods.
The scope stays on describing one study’s setup, results, and interpretation.
Match answer choice verbs and details to the passage
Now compare each choice’s verb (describe, present an analysis critiquing, summarize, argue) and added details to what the passage actually does:
- The passage does not argue for policies.
- It does not criticize existing methods.
- It does not say the behavior was unexpected or that scientists had to rethink song function.
- It does briefly report what a study found about timing changes in whale songs near shipping noise, and what Tran thinks that means.
The only option that accurately matches this neutral, research-reporting purpose and the correct focus on shipping noise and song timing is: “To summarize the findings of a study that examined how shipping noise influenced the timing of humpback whale song components.”