Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're talking about urban heat islands, where cities are significantly warmer than surrounding rural areas. This happens because concrete and asphalt absorb and re-emit heat, while vegetation, which provides shade and releases moisture, is scarce. One solution is green roofs—roofs covered with plants. They reduce heat absorption, improve insulation, and lower energy costs. But there's a catch: green roofs can be expensive to install and maintain, especially on older buildings. Another approach is cool roofs, which use reflective materials to bounce sunlight back. These are cheaper but less effective at cooling the air around them. Interestingly, a study in Melbourne found that combining both—green roofs for insulation and cool roofs for reflection—can maximize benefits. However, the effectiveness depends on climate. In dry regions, green roofs need irrigation, which consumes water. So, cities must weigh costs and local conditions. Now, let's consider a specific case...
❓ 题目 What does the professor identify as a major disadvantage of green roofs in dry climates?
A. They require significant water for irrigation.
B. They reflect too much sunlight, causing glare.
C. They are less effective than cool roofs in all climates.