These are sets of two stars that orbit around a common center of mass.

即由两颗恒星组成的组合，它们围绕一个共同的质心运行。

And usually, these questions come in a set of two, so five options and five options.

通常，这些问题会有两道，所以就是五个选项，再五个选项。

Okay. So six sets of two.

好的。 所以六组两个。

So these three pronouns are actually a little bit less indefinite than most indefinite pronouns because they refer to a set of two things.

所以这三个代词实际上比大多数不定代词的不定代词要少一些，因为它们指的是两个事物的集合。