Listen to part of a lecture in a biology class. Professor: Today we're going to discuss a fascinating adaptation in desert plants. Consider the saguaro cactus, which grows in the Sonoran Desert. It can live over 150 years and reach heights of 15 meters. How does it survive such extreme heat and drought? First, its shallow root system spreads widely, just under the soil surface. This allows it to absorb water quickly after brief rainstorms. Second, the saguaro has pleats, or vertical ridges, that expand like an accordion to store large amounts of water inside its stem. A fully hydrated saguaro can weigh over a ton. Third, it uses a special type of photosynthesis called CAM, where stomata open at night to take in carbon dioxide, reducing water loss during the hot day. But here's the interesting part: saguaros rely on nurse trees, like paloverde, for shade during their early growth. Without this protection, young saguaros would die from heat stress. So, their survival is a combination of physiological and ecological strategies.
❓ 문제 According to the professor, what is one reason saguaro cacti can survive in the desert?
A. They have deep roots that reach underground water.
B. They open their stomata during the day to take in CO2.
C. They store water in their expandable stems.
D. They grow only in the shade of tall trees throughout their lives.
✅ 정답
They store water in their expandable stems.
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
