Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands. This phenomenon occurs when cities are significantly warmer than surrounding rural areas. The main cause is the replacement of natural surfaces with concrete and asphalt, which absorb and retain heat. Additionally, buildings and vehicles generate waste heat. One surprising solution is green roofs—rooftops covered with vegetation. A study in Chicago found that green roofs can reduce rooftop temperatures by up to 40 degrees Fahrenheit in summer. They also reduce stormwater runoff by absorbing rainwater. However, the initial cost of installing a green roof is higher than a traditional roof, but over time, energy savings and extended roof lifespan can offset that expense. Some cities now offer tax incentives to encourage green roof installation. Professor: So, what's the key takeaway? Green roofs are a practical, long-term investment for urban sustainability.
❓ 题目 What is the main purpose of the lecture?
A. To explain why urban heat islands occur and discuss a solution
B. To compare the costs of different types of roofing materials
C. To describe the history of green roof technology in Chicago
D. To argue that urban heat islands are unavoidable
✅ 正确答案
To explain why urban heat islands occur and discuss a solution