Listen to part of a lecture in an environmental science class. Professor: Today we're discussing water pollution, specifically a major cause called eutrophication. Eutrophication occurs when excess nutrients, particularly nitrogen and phosphorus, enter a water body, often from agricultural runoff or untreated sewage. These nutrients cause rapid growth of algae, forming dense blooms on the surface. When the algae die, bacteria decompose them, consuming large amounts of dissolved oxygen. This oxygen depletion can lead to hypoxia, or dead zones, where fish and other aquatic life cannot survive. One famous example is the Gulf of Mexico's dead zone, which forms each summer near the Mississippi River delta. But there are solutions. For instance, farmers can use buffer strips—vegetated areas along waterways—to absorb nutrients before they reach rivers. Also, treating wastewater more effectively can reduce nutrient loads. However, these measures require cooperation among multiple stakeholders, including policymakers, farmers, and communities. So, addressing eutrophication is not just a scientific challenge but also a social and economic one.
❓ Вопрос What is the main cause of eutrophication mentioned by the professor?
A. A rapid increase in water temperature due to climate change
B. An excess of nutrients like nitrogen and phosphorus entering water bodies
C. Overfishing that disrupts the aquatic food chain
D. The introduction of invasive plant species into lakes
✅ Правильный ответ
B. An excess of nutrients like nitrogen and phosphorus entering water bodies
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
