Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about urban heat islands, and specifically, one surprising solution: green roofs. Now, you might think that planting vegetation on rooftops is just about aesthetics, but research shows it can significantly reduce the ambient temperature in cities. How does that work? Well, traditional dark roofs absorb sunlight and re-radiate heat, which increases the local temperature, especially at night. Green roofs, on the other hand, use plants and soil. They reflect more sunlight, and they also cool the air through evapotranspiration—the process where plants release water vapor. This can lower rooftop surface temperatures by up to 40 degrees Celsius compared to a conventional roof. But there's a catch. Green roofs are heavy and require structural support, and they also need regular maintenance, like watering and weeding. So, while they're effective, they're not a one-size-fits-all solution. For existing buildings, retrofitting can be costly. However, for new buildings, incorporating green roofs from the design stage is more practical. So, next time you see a rooftop garden, remember—it's not just pretty; it's doing important environmental work.
❓ 質問 What is the main point the professor makes about green roofs?
A. They are primarily used for aesthetic purposes in urban areas.
B. They help reduce urban temperatures but have practical limitations.
C. They are the most cost-effective solution for all buildings.
D. They are only effective when installed on new buildings.
✅ 正解
They help reduce urban temperatures but have practical limitations.
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
