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 or wind, tidal energy is predictable because it's driven by the gravitational pull of the moon and the sun. However, there are significant challenges. One major issue is the high cost of building tidal barrages, which are essentially dams across estuaries. These structures can disrupt local ecosystems, affecting fish migration and sediment flow. Another challenge is that tidal power plants only generate electricity during tidal surges, which means they're not constant. But there's a newer approach: underwater turbines, similar to wind turbines, placed in tidal streams. These are less invasive and can operate in deeper waters. Still, they require strong currents to be efficient, and maintenance is difficult due to saltwater corrosion. So, while tidal power has potential, it's not a one-size-fits-all solution. We need to weigh the environmental costs against the benefits of clean energy. Any questions?
❓ คำถาม What is the main challenge of tidal barrages mentioned by the professor?
A. A. They are expensive to build and can harm ecosystems.
B. B. They generate electricity only during strong winds.
C. C. They are difficult to maintain due to saltwater.
D. D. They require deep water to operate efficiently.
✅ คำตอบที่ถูกต้อง
A. They are expensive to build and can harm ecosystems.
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