Question 65·Medium·Inferences
To reduce summer heat, city planners planted 1,000 saplings in each of two adjacent districts. Five years later, both districts had similar numbers of surviving trees, but only one district recorded notably cooler afternoon temperatures. In that cooler district, trees had been clustered to cast overlapping shade on sidewalks and the sunlit sides of buildings; in the other, trees were spaced far apart along wide road medians, leaving large gaps in shade at midday. Thermal images showed that shaded pavements and facades were significantly cooler than unshaded ones. Based on this evidence, the planners most reasonably concluded that _____
Which choice most logically completes the text?
For SAT "logical completion" and inference questions, first underline the key comparisons or changes (here, same number of surviving trees but different planting patterns and temperatures). Next, identify the one main difference that could logically explain the outcome. Then scan answer choices and cross out any that (1) contradict stated facts, (2) introduce new causes not mentioned (like different species or materials), or (3) ignore the evidence you were specifically given (such as the thermal images). Choose the option that most directly restates the cause-and-effect relationship supported by the passage, without adding extra assumptions.
Hints
Focus on the key difference between districts
Both districts started with 1,000 saplings and ended up with similar numbers of surviving trees. What, then, is actually different between the district that got cooler and the one that did not?
Pay attention to where the shade falls
Look closely at which surfaces the trees are shading in each district (sidewalks, building sides, or road medians) and when there are gaps in shade.
Use the thermal image information
The passage mentions thermal images. What did these images show about shaded versus unshaded pavements and building facades, and how does that help explain the temperature difference?
Check for new, unsupported ideas
Eliminate any choice that introduces a cause (like survival rates, tree species, or building materials) that the passage never discusses as a difference between the two districts.
Step-by-step Explanation
Identify what stayed the same in both districts
First notice that each district started with 1,000 saplings, and five years later both districts had similar numbers of surviving trees. That means the total number of trees is not the main factor explaining why only one district was cooler.
Identify what was different between the two districts
The key difference is how and where the trees were planted:
- Cooler district: trees were clustered to cast overlapping shade on sidewalks and sunlit sides of buildings.
- Warmer district: trees were spaced far apart along wide road medians, leaving large gaps in shade at midday.
So, the difference is in the arrangement of the trees and which surfaces they shaded.
Use the thermal image evidence
Thermal images showed that shaded pavements and facades were significantly cooler than unshaded ones. This is direct evidence that shade itself lowers temperatures on these surfaces. Since the cooler district has more continuous shade where people and buildings are, it makes sense that it has cooler afternoons.
Match the conclusion to the evidence
The planners need a conclusion that:
- Uses the fact that the number of trees was similar in both districts.
- Uses the fact that only the district with continuous shade on heat-absorbing surfaces (sidewalks, building facades) was cooler.
- Uses the thermal image evidence that shaded surfaces are cooler than unshaded ones.
Choice D says that arranging trees to maximize continuous shade on heat-absorbing surfaces reduces afternoon temperatures more than spacing the same number of trees far apart, which perfectly summarizes these points. So the correct answer is D.