Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising factor that can affect local climate: the color of roofs. Dark roofs absorb more solar radiation, which can raise the temperature of a building and the surrounding air. In cities, this contributes to the 'urban heat island' effect, where urban areas are warmer than nearby rural areas. To combat this, many cities are now encouraging 'cool roofs' – roofs painted white or made of reflective materials. These roofs reflect sunlight, reducing heat absorption. Studies have shown that cool roofs can lower a building's cooling costs by up to 20 percent. They also help reduce smog, because cooler air slows the chemical reactions that create ground-level ozone. However, cool roofs are not a panacea. In colder climates, they might increase heating costs in winter, since less heat is absorbed. Therefore, the decision to install a cool roof depends on the local climate and the balance between cooling and heating needs.
❓ Câu hỏi What is the main purpose of the lecture?
A. To explain the causes of the urban heat island effect
B. To discuss the benefits and limitations of cool roofs
C. To compare the costs of heating and cooling in different climates
D. To describe the chemical reactions that cause smog
✅ Đáp án đúng
To discuss the benefits and limitations of cool roofs
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
