Question 152·Medium·Inferences
In 2021, urban climatologists studied 18 neighborhoods in a coastal city to test two heat-mitigation strategies: installing highly reflective "cool roofs" and expanding street-tree canopy. Neighborhoods that received both cool roofs and new trees experienced afternoon sidewalk temperatures 3–4°C lower than before; neighborhoods that received only cool roofs showed little change in afternoon sidewalk temperatures compared with areas that received neither intervention. Nighttime temperatures were similar across all neighborhoods. During heat waves, heat-related ambulance calls declined by 18% in areas with both interventions but did not change in areas with only cool roofs.
Therefore, the climatologists inferred that the added reduction in heat-related risk most likely _____
Which choice most logically completes the text?
For inference questions like this, first underline the key comparisons and results (which group changed, which did not, and when). Then restate in your own words what the evidence shows about cause and effect, focusing on what is different between groups that did and did not show improvement. Finally, eliminate answer choices that invent new information, contradict the data, or focus on the wrong time frame, and select the one that matches the pattern described in the passage.
Hints
Focus on the data pattern
Compare what happened in neighborhoods with both interventions to those with only cool roofs and those with neither. Which group actually showed lower afternoon temperatures and fewer ambulance calls?
Pay attention to daytime vs. nighttime
Notice how the passage separates afternoon sidewalk temperatures from nighttime temperatures. Ask yourself: At which time of day did the neighborhoods differ, and how does that connect to heat-related emergencies?
Ask what factor is unique to the successful group
The areas with reduced ambulance calls had two interventions. Which intervention did they have that the "only cool roofs" areas did not have, and how could that logically reduce heat-related risk?
Step-by-step Explanation
Identify the key results in the study
First, restate the important findings:
- Neighborhoods with both cool roofs and new trees had afternoon sidewalk temperatures 3–4°C lower than before.
- Neighborhoods with only cool roofs showed little change in afternoon temperatures compared with areas with neither intervention.
- Nighttime temperatures were similar across all neighborhoods.
- During heat waves, heat-related ambulance calls declined by 18% only in areas with both interventions; calls did not change in areas with only cool roofs.
Understand what needs to be inferred
The conclusion says: "Therefore, the climatologists inferred that the added reduction in heat-related risk most likely ..." This means we need to explain why areas with both interventions (cool roofs + trees) had lower risk (fewer ambulance calls) than areas with only cool roofs or no intervention. We are not being asked what happened, but what likely caused that added benefit.
Compare the intervention groups to isolate the cause
Look at what is different between the groups:
- Both groups ("both" and "only cool roofs") had cool roofs, but only the "both" group also had new trees.
- Only the "both" group showed: (1) cooler afternoon sidewalks, and (2) fewer heat-related ambulance calls.
- Nighttime temperatures were similar everywhere, so the difference in risk is probably not about nighttime heat. This suggests that the extra change (lower afternoon temperatures and fewer calls) is tied to the trees, not just the roofs or nighttime conditions.
Match the correct causal explanation to the answer choices
Now choose the option that best explains the added reduction in heat-related risk in the neighborhoods with both interventions:
- It cannot be about nighttime cooling, because nighttime temperatures were similar everywhere.
- It cannot be that cool roofs alone are sufficient, because areas with only cool roofs saw no change in ambulance calls.
- There is no mention of population changes. The only answer that fits the evidence is that the expanded tree canopy, through its daytime shading and evaporative cooling, caused the added reduction in heat-related risk.
Correct answer: resulted from the daytime shading and evaporative cooling provided by the expanded tree canopy.