It's up in the air.

尚未确定。

It's hard to say.

难说。

It's a matter of life and death.

事关生死。

It was eleven o'clock when he finally showed up.

他最后露面时，已经11点钟了。

I think the teacher works us too hard.

我觉得教师害得我们太苦了。

If you consider that she's only been studying English a year, she speaks it very well.

你可以考虑到她那学一年的英语，她的英语说得非常好。