Listen to part of a lecture in an environmental science class.
Today we're going to talk about urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. One major cause is the replacement of natural surfaces with asphalt and concrete, which absorb and retain heat. Another factor is the lack of vegetation, since trees and plants provide shade and release moisture through evapotranspiration. To combat this, many cities are implementing green roof initiatives. A green roof is a rooftop covered with vegetation and a growing medium. These roofs can lower surface temperatures by up to 40 degrees Celsius compared to conventional roofs. They also reduce stormwater runoff by absorbing rainwater, and they improve air quality by filtering pollutants. However, the initial installation cost is higher than traditional roofing, which is a barrier for some building owners. Nevertheless, over time, the energy savings from reduced cooling needs can offset the upfront expense. So, while the initial investment may seem steep, the long-term benefits are substantial.
❓ Question What is the main purpose of the lecture?
A. To explain the causes of urban heat islands and describe a solution
B. To compare the costs of different roofing materials
C. To argue that green roofs are too expensive
D. To discuss the history of city planning
✅ Correct Answer
To explain the causes of urban heat islands and describe a solution
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word
