我不知道他在谈什么。

I didn't know what he was talking about.

《牛津词典》

我不知道还能再说点什么。

I didn't know what else to say.

《柯林斯英汉双解大词典》

我不知道接着该做什么了。

I don't know what to do next.

《柯林斯英汉双解大词典》

Now,the problem with this is that Papias and these other people didn't really know what they were talking about.

问题是帕皮亚和其他人,根本不知道自己在说什么。

耶鲁公开课 - 新约课程节选

I chose English Literature because when I started off a university, I didn't know what it was I wanted to do.

我选英语文学是因为当我刚上大学的时候，我不知道自己到底想做什么。

为何选那门专业？ - SpeakingMax英语口语达人

We've had a great deal to do with it, but of course we still haven't the slightest idea what it is.

我们花了很大的功夫来接解决这个问题，但我们仍然一点都不知道语言是什么。

耶鲁公开课 - 文学理论导论课程节选