because引导的是什么从句

例句：

They are here because of us.

他们是因为我们来这里的。

We couldn't understand them because they were talking in Chinese.

我们听不懂他们在讲些什么，因为他们说的是汉语。

His school work is suffering because of family problems.

由于家庭问题，他的学业日渐退步。

Two players are out of the team because of injury.

两名队员因伤退出了比赛。

Why get upset just because you got one bad grade?

何必因为一次成绩不好就想不开呢？