Questions 1–4 are based on the following passage.
The Hidden Work of City Trees
(1) On a July afternoon, the asphalt in a downtown parking lot can grow far hotter than the grass beneath a nearby oak, sometimes by dozens of degrees. This difference is one reason scientists describe many cities as “heat islands.” Pavement, rooftops, and brick absorb sunlight during the day and release it slowly at night, so urban neighborhoods often stay warmer than the countryside around them.
(2) Trees counter this effect in two ways. First, their canopies block sunlight before it reaches the ground. Second, through a process called transpiration, trees draw water from the soil and release it as vapor through their leaves. As that water evaporates, it carries heat away, much as sweat cools a runner’s skin.
(3) The benefits do not stop at temperature. Tree roots and leaves slow rainwater so that less of it rushes into storm drains at once, and leaves trap some of the dust and soot that drift through city air.
(4) Yet trees are not spread evenly. In many cities, lower-income neighborhoods have far fewer street trees than wealthier ones, which means the residents who can least afford air conditioning often face the hottest summers. For that reason, a growing number of city planners now treat tree planting not as decoration but as a matter of public health.
Which statement best expresses the central idea of the passage?
Show answer and explanation
Answer: D. Trees ease several problems of city life, so planners increasingly view them as essential to public health.
Each paragraph builds toward the idea that trees cool cities, manage stormwater, and clean air, and the final sentence states that planners now see them as a public-health matter. The choice about air conditioners misreads paragraph 4, which uses the lack of air conditioning to show why trees matter, not to propose a substitute.