Listen to part of a lecture in a biology class. The professor is discussing animal communication.
Professor: Today, we're going to talk about a fascinating aspect of animal behavior: communication. Now, when we think of communication, we often think of sound, like birdsong or the calls of primates. But many animals rely on visual signals. For example, the peacock's elaborate tail is a classic visual signal used to attract mates. However, visual signals have a limitation: they require light and a clear line of sight. In dense forests or at night, they're not very effective. That's where chemical signals come in. Many insects, like ants and moths, release chemical substances called pheromones. These chemicals can travel long distances and work even in complete darkness. For instance, female moths emit a specific pheromone that males can detect from miles away using their sensitive antennae. This is incredibly efficient for finding a mate in a sparse environment. But chemical signals also have downsides. They can be slow to disperse, and they might attract predators. So, animals often use a combination of signals depending on the situation. Does anyone have a question so far?
❓ 문제 What is the main limitation of visual signals in animal communication?
A. A. They are not effective in dense forests or at night.
B. B. They are too slow to travel long distances.
C. C. They require too much energy to produce.
D. D. They can only be used by insects.
✅ 정답
A. They are not effective in dense forests or at night.
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
