Listen to part of a lecture in an environmental science class.
Professor: Today we're going to talk about urban heat islands, a phenomenon where cities are significantly warmer than surrounding rural areas. This happens because concrete, asphalt, and buildings absorb and re-emit heat from the sun more than natural landscapes like forests or grasslands. Also, waste heat from vehicles and air conditioners adds to the effect.
Now, one common solution is planting more trees, which provide shade and cool the air through evapotranspiration. But there's another approach: cool roofs. These are roofs coated with reflective materials that bounce sunlight back into the atmosphere. Studies have shown that cool roofs can reduce a building's cooling costs by up to 15 percent. However, they have a limitation—they mainly work during the day. At night, the stored heat in walls and streets still radiates, so the effect is smaller.
So, while cool roofs are useful, they are not a complete fix. A combination of strategies is often needed.
❓ Pregunta What limitation of cool roofs does the professor mention?
A. They are too expensive for most buildings.
B. They are less effective at night because of stored heat.
C. They require constant maintenance.
D. They only work in dry climates.
✅ Respuesta correcta
They are less effective at night because of stored heat.
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