起初，玛丽还不知道那是什么。

At first she could not tell what it was.

youdao

她不知道那是什么，因为起初她几乎不能把它和风本身区别开来。

She did not know what it was, because at first, she could scarcely distinguish it from the wind itself.

youdao

她不知道那是什么滋味，我心想。

She doesn't know what it's like, I thought.

youdao

If you don't have the units, then if you say the answer is 19, then we don't know what it means.

如果没有的话,比如你的答案是十九,那我们就不知道这是什么意思

耶鲁公开课 - 基础物理课程节选

And you remember Yeats in "The Second Coming," - there's a beast that's kind of-- He doesn't know what it is, and here he's saying something similar.

你们记得在二次圣临里“,有提到一只野兽-,他不知道那到底是什么，在此他表达相似的想法。

耶鲁公开课 - 现代诗歌课程节选

He mentioned the Nicomachean Ethics which I have never read I don't know what that is.

他提到了《尼各马克伦理学》,一本我从没读过的书，我不知道那本书是讲什么的。

耶鲁公开课 - 金融市场课程节选