Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising ally in the fight against climate change: beavers. Now, you might think of beavers as simple dam builders, but their impact on ecosystems is profound. When beavers build dams, they create ponds and wetlands. These wetlands slow down water flow, allowing sediment and pollutants to settle. This natural filtration improves water quality downstream. But here's the key point: the ponds also store large amounts of carbon. Organic matter, like leaves and wood, sinks to the bottom and, because the water is low in oxygen, it decomposes very slowly. This means carbon is locked in the sediment for centuries. In fact, research suggests that beaver ponds can sequester up to 12 times more carbon than a comparable area of grassland. So, instead of viewing beavers as pests, some conservationists now propose reintroducing them to restore degraded river systems. This not only boosts biodiversity but also helps mitigate climate change. However, beaver activity can cause flooding in agricultural areas, so careful management is needed. Any questions?
❓ 문제 What is the main point the professor makes about beavers?
A. Beavers are primarily a nuisance to farmers.
B. Beavers' dam-building helps improve water quality and store carbon.
C. Beavers are being removed from river systems to prevent flooding.
D. Beaver ponds do not significantly affect the surrounding environment.
✅ 정답
Beavers' dam-building helps improve water quality and store carbon.
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