Listen to part of a lecture in an environmental science class. Professor: Today we're going to discuss a surprising factor in urban heat islands. You might think that planting more trees would always lower city temperatures, but recent research shows that the type of tree matters a lot. Some trees, like oaks, have broad leaves that provide shade and release water vapor through transpiration, which cools the air. However, other trees, such as certain pines, have dense canopies that trap heat and emit volatile organic compounds, or VOCs. These VOCs can react with pollutants to form ozone, a greenhouse gas. In a study comparing two city blocks in Los Angeles, the block with large deciduous trees was several degrees cooler than the block with evergreen pines. The researchers concluded that while all trees help absorb carbon dioxide, their microclimatic effects vary. So city planners should prioritize species that maximize cooling, especially in hot climates. This is not just about aesthetics; it's about public health, as extreme heat is a leading cause of weather-related deaths.
❓ Pregunta What is the main point the professor makes about trees in urban areas?
A. A. All trees are equally effective at reducing city temperatures.
B. B. The cooling effect of trees depends on their species and characteristics.
C. C. Evergreen pines are better than oaks for cooling because they are denser.
D. D. Trees should be planted mainly for their aesthetic value in cities.
✅ Respuesta correcta
B. The cooling effect of trees depends on their species and characteristics.
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