Narrator: Listen to part of a lecture in an environmental science class. Professor: Today, let's talk about urban heat islands. As you know, cities tend to be warmer than surrounding rural areas. This is mainly because concrete and asphalt absorb and re-radiate heat more than vegetation does. But there are solutions. One effective strategy is planting more trees, which provide shade and release moisture through transpiration. Another is using reflective materials on rooftops, often called cool roofs. These materials reflect sunlight instead of absorbing it, reducing the need for air conditioning. Interestingly, a study in Los Angeles found that a combination of cool roofs and street trees could lower city temperatures by up to 3 degrees Celsius. However, there is a trade-off: cool roofs reflect heat upward, which might actually increase temperatures for pedestrians at street level. So, urban planners must weigh the benefits and drawbacks carefully. Now, let's consider how these strategies might be adapted to different climates.
❓ 题目 What is the professor's main point about cool roofs?
A. They are always more effective than planting trees.
B. They have potential drawbacks despite their benefits.
C. They are not recommended for hot climates.
D. They work best when used alone in urban areas.
✅ 正确答案
They have potential drawbacks despite their benefits.
