第二群体指的是两个或两个以上的人，他们处于一种非个人的关系中，因一个特定的、实际的目的走到一起。

A secondary group entails two or more people who are involved in an impersonal relationship and have come together for a specific, practical purpose.

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这是二甲醚的结构异构体。

It is a constitutional isomer of dimethyl ether.

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这是一种性别决定的方法，叫做单倍二倍体。

This is a method of sex determination known as haplodiploidy.

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