Listen to part of a lecture in an environmental science class. Professor: Today, we’re going to discuss a surprising factor that affects urban temperatures: rooftop gardens. Now, you might think that green roofs primarily reduce energy costs by insulating buildings, and that’s true. But recent research suggests that their cooling effect extends beyond the building itself. When many rooftops in a city are covered with vegetation, they collectively lower the ambient air temperature. This happens because plants release moisture through transpiration, which cools the air, much like sweat cools our bodies. In a study in Toronto, researchers found that if green roofs covered even five percent of buildings in a downtown area, the local temperature could drop by up to two degrees Celsius. That might sound small, but it can reduce the formation of smog and decrease the demand for air conditioning, creating a feedback loop. However, the effectiveness depends on the climate. In dry regions, green roofs might require significant irrigation, offsetting their benefits. So, while green roofs are promising, urban planners must assess local conditions before implementing them on a large scale.
❓ Вопрос What is the main point the professor makes about rooftop gardens?
A. They are too expensive for most cities to implement.
B. They can lower city temperatures, but their effectiveness varies by climate.
C. They primarily help individual buildings rather than the whole city.
D. They require constant irrigation in all environments.
✅ Правильный ответ
They can lower city temperatures, but their effectiveness varies by climate.
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
