Question 47·Medium·Central Ideas and Details
Urban ecologist Dr. Lila Hernandez had long suspected that the small patches of greenery scattered throughout major cities offered more than aesthetic value. Her 2019 study tracked the daily movements and heart-rate variability of 1,200 residents of three metropolitan areas. She found that even brief, routine exposure to street trees—walking past them on the way to work, for instance—corresponded with measurable reductions in stress. Hernandez argues that the findings should prompt city planners to treat trees as essential infrastructure rather than optional beautification. Subsequent articles in planning journals have cited her work as evidence that public health and urban design are intertwined.
Which choice best states the central idea of the passage?
For central idea questions, first read the entire passage and quickly summarize it in your own words, focusing on the author’s main finding or claim and any key implication. Then, look for the answer that captures both the overall result and the author’s main conclusion or argument, not one that only mentions methods or a single detail. Eliminate choices that introduce ideas not in the passage (like cost, motives, or extreme claims) or that focus too narrowly on one part of the text. When in doubt, check whether each option would still make sense as a one-sentence label for the whole passage; if it wouldn’t, cross it out.
Hints
Focus on the big picture
Before looking at the choices, summarize in one sentence what Hernandez’s study found and what she wants city planners to do with that information.
Use the beginning and end of the passage
Look closely at the first sentence (what she suspected and studied) and the sentences that mention what she argues and how planning journals use her work—those usually point to the central idea.
Watch for added or twisted information
Check each answer for words or ideas that don’t appear in the passage, like specific motives (for example, cost) or strong claims about what planners used to do; answers that introduce new ideas are usually wrong.
Ask: is this the whole story or just a detail?
Eliminate any choice that only talks about the methods of the study or one small part of the passage, instead of both the research findings and their broader implication.
Step-by-step Explanation
Identify the task
The question asks for the central idea of the passage. That means you need the one sentence that best captures what the whole paragraph is mainly about, not a small detail or an extra claim.
Summarize the passage in your own words
Quickly restate the passage:
- Hernandez suspected city greenery did more than just look nice.
- Her 2019 study tracked movements and heart-rate variability of many city residents.
- She found that even brief exposure to street trees was linked to reduced stress.
- She argues planners should treat trees as essential infrastructure (not just decoration).
- Planning journals now cite her work as evidence that public health and urban design are connected.
So overall, it’s about what her research shows and how it should affect city planning.
Decide what a correct central idea must include
A good central idea statement should:
- Mention what the research found (not just how it was done).
- Capture that the finding is about health benefits (reduced stress).
- Include the implication for city planning (trees as essential infrastructure / priority in planning).
- Avoid adding claims not mentioned in the passage (like cost or long-term history of planners) or focusing only on a small detail.
Evaluate each answer choice against the passage
Now compare each choice to the summary and requirements:
- A talks only about tracking residents and misstates the goal of the study (it was about stress, not commuting patterns).
- B adds an extreme claim that planners ignored evidence until 2019, which the passage never says.
- D claims planting street trees is the most cost-effective method to reduce stress; cost is never mentioned.
- C correctly states that Hernandez’s research shows city trees provide real health benefits and argues they should be prioritized in urban planning, matching both the findings and her argument.
Therefore, the best answer is C) Hernandez's research shows that city trees provide tangible health benefits and should be prioritized in urban planning.