Question 29·Medium·Central Ideas and Details
Urban ecologist Dr. Priya Desai investigated whether street trees can lessen neighborhood noise in a densely populated Indian city. For six months, her team recorded decibel levels on thoroughfares lined with recently planted neem and banyan trees and on similar streets without trees. The tree-lined blocks averaged a 5-decibel drop—enough for most pedestrians to notice—though the researchers found the relief was strongest within ten meters of the trees. Desai emphasized that additional work is needed to determine how different species and traffic patterns influence the results.
Which choice best states the main idea of the text?
For main-idea questions, first quickly paraphrase the passage in one short sentence: who did what, and what was the main result or point? Then scan the answer choices and eliminate any that (1) add strong words like “only,” “primarily,” or “unchanged” that the passage never supports, (2) focus on a side detail rather than the main finding, or (3) contradict the passage’s overall conclusion or tone. The correct choice will accurately reflect both the core result and any important limits or conditions mentioned, without exaggeration or new information.
Hints
Find the research question
Look at the first sentence: what was Desai investigating overall? Your answer should reflect that broad purpose, not a small detail.
Focus on the main result, not side notes
Pay close attention to the sentence about the 5-decibel drop and where the relief was strongest. How do these details describe the outcome of the study?
Watch out for extra claims
Check each answer choice for words like “only,” “rather than,” or “unchanged.” Does the passage actually say these strong claims, or does it just mention the ideas more cautiously?
Think about scope and limits
Ask yourself: does the passage present the findings as absolute and final, or as limited and needing more research? Choose the option that matches this tone.
Step-by-step Explanation
Restate what the study was about
First, summarize the passage in your own words.
- Desai investigated whether street trees reduce neighborhood noise in a crowded city.
- Her team compared noise levels on streets with neem and banyan trees to similar streets without trees.
- This shows the main focus is on the effect of street trees on noise.
Identify the key findings and limits
Next, pick out the main results and any limits on those results.
- The tree-lined blocks had an average 5-decibel drop, which the passage says is enough for most pedestrians to notice. That means the effect is real and measurable.
- The passage also says the relief was strongest within ten meters of the trees, so the benefit is limited in range, not citywide or across the whole street.
- Desai adds that more work is needed to see how different species and traffic patterns affect the results. That signals that her conclusion is tentative and specific to this setup, not absolute or final.
Compare each answer choice to the passage
Now, evaluate how well each option matches the overall idea of the passage, not just one detail.
- One wrong choice claims that only neem and banyan work. The passage never says that; it only says those are the trees studied.
- Another wrong choice says traffic patterns, rather than tree cover, mainly cause noise changes. The passage does not say that; it only says more work is needed to understand traffic patterns.
- A third wrong choice focuses on the effect persisting unchanged for six months, but the passage only tells us the study lasted six months, not that the effect stayed the same the whole time.
- The remaining choice is the only one that mentions both the noise reduction and its limited distance without adding extra claims.
Select the answer that captures the main idea
Because the passage’s central message is that Desai’s study found a noticeable drop in noise on tree-lined streets, especially close to the trees, and that this benefit doesn’t extend very far, the best statement of the main idea is:
Desai’s study showed that planting street trees can measurably reduce neighborhood noise, although the effect is limited in range.