by yourself

adv. 单独地, 独立地

例句与用法：

How long were you by yourself in the classroom?

你独自一人在教室里多长时间了?

Are you sure you did this exercise by yourself?

这个练习真是你自己做的吗?

Since you are already of age now, you should solve the problems by yourself.

你已经成年了，这些问题要自己解决。

You can't go mountain climbing by yourself.

你不能自己去登山。

I believe that you can work out this problem by yourself.

我相信你自己能做出这道题的。