Pregunta 1 de 36
The Quiet Work of City Trees
(1) On a hot July afternoon, the difference between a street with trees and a street without them can be felt through the soles of your shoes. Researchers who measure surface temperatures have found that shaded sidewalks and pavement can be many degrees cooler than the same surfaces in full sun. That simple fact is one reason a growing number of cities now treat trees not as decoration but as basic equipment, in the same category as storm drains and streetlights.
(2) Trees cool a city in two ways. First, their leaves block sunlight before it can heat roads, roofs and parking lots. Second, trees release water vapor through their leaves, a process called transpiration. As that water evaporates, it carries heat away from the surrounding air, much as sweat cools a person's skin.
(3) The benefits do not stop at temperature. Tree roots and the soil around them soak up rainwater, which slows the flow into storm drains during heavy storms. Leaves trap some dust and other particles from the air. And several studies have linked tree-lined streets with higher home values and with residents who report feeling less stressed.
(4) Yet the shade is not shared equally. In many American cities, neighborhoods with lower incomes have noticeably fewer trees than wealthier areas nearby. Some of this gap goes back decades, to choices about where to build highways, factories and parks. Because these same neighborhoods often have more pavement and fewer air-conditioned homes, residents can face greater danger during heat waves.
(5) Planting trees is not a quick fix. A young tree may need ten years or more before it casts meaningful shade, and it needs regular watering while its roots grow. Trees planted without a care plan often die within a few years. For that reason, city foresters increasingly say that the real measure of a program is not how many trees are planted, but how many are still alive and growing a decade later.
(6) The cities making the most progress tend to combine three things: careful mapping to find the streets with the least shade, long-term funding for watering and pruning, and partnerships with residents who help care for the trees on their blocks. Done well, a tree program becomes a gift that grows more valuable every year.
Which statement best expresses the central idea of the passage?
Pista
The central idea must cover every paragraph, not just one. Try saying the main point in your own words before you look at the choices.
Solución paso a paso
Where the answer comes from: each paragraph adds one piece. Paragraph 1 says cities now treat trees "as basic equipment." Paragraphs 2 and 3 explain the benefits (cooling, rainwater, cleaner air). Paragraph 4 says "the shade is not shared equally." Paragraphs 5 and 6 explain that planting "is not a quick fix" and that success depends on long-term care.
Step by step:
- Ask what the whole passage is about: the value of city trees.
- Ask what the author says about that topic: trees are valuable, but the benefits depend on fair placement and long-term care.
- Test each choice with the umbrella test — does every paragraph fit under it?
Only choice B covers the benefits, the unequal shade and the need for long-term care. Choice A is one detail from paragraph 2. Choice C overstates paragraph 4. Choice D twists paragraph 5, which says planting alone is not enough — not that planting is a waste.
Tip: the central idea is the broadest accurate statement. Eliminate choices that cover only one paragraph or that use stronger words than the text.
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