Narrator: Listen to part of a lecture in an environmental science class.
Professor: Today we're going to talk about urban heat islands—areas in cities that are significantly warmer than surrounding rural areas. One major cause is the replacement of natural surfaces with materials like concrete and asphalt, which absorb and retain heat. Another factor is the lack of vegetation, since trees and plants provide shade and release moisture through transpiration. But here's an interesting solution: green roofs. A green roof is a rooftop covered with plants and a growing medium. These roofs can reduce surface temperatures by up to 40 degrees Fahrenheit compared to conventional roofs. They also improve insulation, lowering heating and cooling costs. However, installation costs are higher, and not all buildings can support the weight of a green roof. Some cities are offering tax incentives to encourage their adoption. While green roofs aren't a complete solution, they represent a promising step toward mitigating the urban heat island effect.
❓ 题目 What is the main purpose of the lecture?
A. A. To explain the causes of urban heat islands and propose green roofs as a partial solution.
B. B. To argue that green roofs are too expensive and impractical for most cities.
C. C. To describe the history of green roof technology in Europe.
D. D. To compare urban heat islands with other climate phenomena.
✅ 正确答案
A. To explain the causes of urban heat islands and propose green roofs as a partial solution.