题目原文：
A huge marine mammal known as Steller’s sea cow once lived in the waters around Bering Island off the coast of Siberia. It was described in 1741 by Georg W. Steller, a naturalist who was among the first Europeans to see one. In 1768 the animal became extinct. The reasons for the extinction are not clear. Here are three theories about the main cause of the extinction.
First, the sea cows may have been overhunted by groups of native Siberian people. If this theory is correct, then the sea cow population would have originally been quite large, but hundreds of years of too much hunting by the native people diminished the number of sea cows. Sea cows were a good source of food in a harsh environment, so overhunting by native people could have been the main cause of extinction.
Second, the sea cow population may have become extinct because of ecosystem disturbances that caused a decline in their main source of food, kelp (a type of sea plant). Kelp populations respond negatively to a number of ecological changes. It is possible that ecological changes near Bering Island some time before 1768 caused a decrease of the kelp that the sea cows depended on.
Third, the main cause of extinction of the sea cows could have been European fur traders who came to the island after 1741. It is recorded that the fur traders caught the last sea cow in 1768. It thus seems reasonable to believe that hunting by European fur traders, who possessed weapons that allowed them to quickly kill a large number of the animals, was the main cause of the sea cow’s extinction.
题目音频：
学术写作：
教授：朋友而言，有亲密的小圈子还是丰富的大圈子，对一个人的身心健康更好？
Andrew：亲密的小圈子更好。
Claire：丰富的大圈子更好。
Doctor Achebe: Let’s explore the dynamics of social interactions and their impact on our well-being. Socializing in smaller groups versus larger circles can have varying effects on one’s health and happiness. Some argue that smaller groups foster deeper connections, allowing for more meaningful interactions and a sense of closeness. Conversely, larger friend circles offer diversity and exposure to different perspectives. Which do you think contributes more to a person’s health and happiness: spending time with a close-knit few or a larger group of friends?
Andrew: Developing strong bonds with a few close friends fosters deeper connections and enhances emotional support. These intimate relationships often lead to increased trust and understanding, allowing for genuine empathy and shared experiences. Small friend groups offer a sense of security and authenticity in interactions, promoting mental well-being.
Claire: Having a wide circle of friends offers diverse perspectives and experiences, enriching one’s social life. Numerous friendships provide a larger support network, creating opportunities for various activities and interests. Engaging with a larger group cultivates adaptability, social skills, and exposure to different cultures or ideas, contributing to personal growth.
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