Listen to part of a lecture in an environmental science class. Professor: Today we're discussing urban heat islands—why cities are often warmer than surrounding rural areas. One major factor is the replacement of natural surfaces with materials like concrete and asphalt, which absorb and retain heat. Another is the lack of vegetation, since trees provide shade and release moisture through transpiration. But there's a less obvious contributor: waste heat from buildings, vehicles, and air conditioning units. In fact, studies show that air conditioning can increase outdoor temperatures by up to one degree Celsius in dense city centers. This creates a feedback loop—hotter air makes people use more AC, which generates more heat. To combat this, some cities are implementing cool roofs, which reflect solar radiation, and green roofs, which are covered with plants. These strategies not only lower surface temperatures but also reduce energy demand. The challenge is cost and maintenance, but long-term benefits are significant.
❓ Вопрос What does the professor identify as a less obvious cause of urban heat islands?
A. The use of dark-colored building materials
B. Heat released from air conditioning units
C. Reduced tree cover in city parks
D. Increased solar radiation in urban areas
✅ Правильный ответ
Heat released from air conditioning units
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