Narrator: Listen to part of a lecture in an environmental science class. Professor: So we've been talking about renewable energy sources, and today I want to focus on tidal power. Unlike solar and wind, tidal energy is predictable because it depends on the gravitational pull of the moon and the sun, which we can calculate in advance. However, there are significant challenges. The most common method is building a tidal barrage, which is essentially a dam across a bay or estuary. When the tide comes in, water flows through turbines, generating electricity. But barrages can disrupt local ecosystems. They change the salinity levels and sediment flow, which affects fish and birds that rely on the intertidal zone. An alternative is tidal stream generators, which work like underwater wind turbines. They're less invasive but currently more expensive and harder to maintain due to saltwater corrosion. So while tidal power offers reliability, we must weigh its environmental costs and economic feasibility. Any questions?
❓ 문제 What is the professor's main point about tidal power?
A. A) Tidal power is the most cost-effective renewable energy source.
B. B) Tidal power is reliable but faces environmental and economic challenges.
C. C) Tidal barrages are the only viable method to generate tidal energy.
D. D) Tidal stream generators have no negative impact on marine life.
✅ 정답
B) Tidal power is reliable but faces environmental and economic challenges.
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