Narrator: Listen to part of a lecture in an environmental science class. Professor: Today, let's discuss urban heat islands. As you know, cities tend to be warmer than surrounding rural areas. This is mainly because concrete and asphalt absorb and retain heat, while vegetation, which provides shade and releases moisture, is scarce. But there are strategies to mitigate this effect. One effective approach is installing green roofs—roofs covered with plants. These roofs not only absorb sunlight but also cool the air through evapotranspiration. Another strategy is using cool pavements, which are designed to reflect more sunlight and absorb less heat. However, cool pavements can be costly and may require frequent maintenance. Interestingly, a study in Phoenix found that combining green roofs with cool pavements reduced local temperatures by up to 3 degrees Celsius. But the researchers noted that the cooling effect was most significant during the day, and at night, the difference was minimal. So, while these measures help, they are not a complete solution. More comprehensive planning, such as increasing tree canopy and altering building designs, is also needed.
❓ 题目 What does the professor say about the cooling effect of green roofs and cool pavements in Phoenix?
A. A. It was greater during the day than at night.
B. B. It was observed only in the summer months.
C. C. It was more effective in rural areas.
D. D. It was consistent throughout the day and night.