Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we’re going to talk about a surprising solution to water pollution: constructed wetlands. Now, these aren’t natural wetlands. They’re man-made systems that mimic the natural processes of marshes and swamps. The idea is simple—water, especially agricultural runoff, is full of nitrates and phosphates from fertilizers. When this water flows into rivers, it causes algal blooms that kill fish. But in a constructed wetland, we deliberately plant certain aquatic plants, like cattails and reeds, and their roots provide a home for bacteria. These bacteria break down the nitrates and phosphates, removing them from the water before it reaches the river. The process is passive—it doesn’t require energy or chemicals. And here’s the kicker: these wetlands also provide habitat for birds and other wildlife. So, they’re not just cleaning water; they’re restoring ecosystems. However, they do require land and time to mature. A well-designed wetland might take two to three years to reach full efficiency. But after that, it can operate for decades with minimal maintenance. So, the question is, why aren’t we using them everywhere?
❓ 質問 What is the main advantage of constructed wetlands mentioned by the professor?
A. A. They require no land and can be built anywhere quickly.
B. B. They use natural processes to remove pollutants without chemicals or energy.
C. C. They completely eliminate the need for fertilizers in agriculture.
D. D. They are cheaper than any other water treatment method.
✅ 正解
B. They use natural processes to remove pollutants without chemicals or energy.
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
