Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising contributor to greenhouse gas emissions—rice paddies. Now, we often think of carbon dioxide as the main culprit, but rice cultivation releases significant amounts of methane. Methane is actually more potent than CO2 in trapping heat, though it doesn't last as long in the atmosphere. The reason rice paddies produce methane is that they are flooded. When soil is underwater, oxygen is depleted, and anaerobic bacteria break down organic matter, releasing methane. However, farmers can reduce this by draining fields periodically. This practice, called alternate wetting and drying, allows oxygen into the soil, preventing methane production. But there's a trade-off. Draining fields might reduce methane but could increase nitrous oxide, another greenhouse gas. So it's a delicate balance. Researchers are now studying new rice varieties that produce less methane, as well as methods to improve water management to minimize overall emissions.
❓ Pregunta What is the main topic of the lecture?
A. A. The role of carbon dioxide in global warming
B. B. How rice cultivation contributes to methane emissions and potential solutions
C. C. The benefits of flooding rice paddies for crop growth
D. D. The comparison of methane and nitrous oxide as greenhouse gases
✅ Respuesta correcta
B. How rice cultivation contributes to methane emissions and potential solutions
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
