Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising solution to urban flooding: green roofs. Now, traditional roofs are impermeable—they shed water quickly, which can overwhelm drainage systems. Green roofs, on the other hand, are covered with vegetation and soil. They act like a sponge. When it rains, the soil absorbs water, and plants take up moisture through their roots. This slows down the runoff. In fact, studies have shown that green roofs can retain up to sixty percent of rainfall during a storm. But there's an even bigger benefit. Because the plants release water vapor through transpiration, they cool the building below. This reduces the need for air conditioning, cutting energy costs. And on a city scale, green roofs can mitigate the heat island effect, where urban areas are warmer than surrounding rural areas. So, while the initial installation cost is higher than a conventional roof, the long-term savings and environmental benefits make it a wise investment. Does anyone have a question?
❓ 문제 What is the main reason the professor says green roofs help reduce urban flooding?
A. A. They cool the building and reduce energy use.
B. B. They slow down the release of rainwater through absorption.
C. C. They are cheaper to install than traditional roofs.
D. D. They increase the heat island effect in cities.
✅ 정답
B. They slow down the release of rainwater through absorption.
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