Listen to part of a lecture in an environmental science class. Professor: Today we're discussing the concept of 'green roofs,' which are rooftops covered with vegetation and soil. While they may seem like a modern trend, green roofs have ancient roots, like the famous Hanging Gardens of Babylon. But their modern appeal lies in their ability to mitigate urban heat islands. You see, conventional dark roofs absorb heat, raising city temperatures. Green roofs, however, reflect less heat but cool the air through evapotranspiration—water evaporating from plants. This process can lower roof surface temperatures by up to 40 degrees Fahrenheit. Beyond temperature control, green roofs also manage stormwater. They absorb rainwater, reducing runoff that can overwhelm sewer systems. Now, one challenge is the initial cost, which is higher than traditional roofing. But over time, green roofs extend roof lifespan and reduce energy bills, making them economically viable. So, despite upfront expenses, the long-term benefits are significant.
❓ Question According to the professor, how do green roofs help mitigate the urban heat island effect?
A. By reflecting more sunlight than conventional roofs
B. By cooling the air through water evaporation from plants
C. By absorbing heat and storing it in the soil
D. By providing shade to the building below
✅ Correct Answer
By cooling the air through water evaporation from plants
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
