The question caught her completely off-guard and she did not know how to reply.

这个问题令她猝不及防，不知道怎么回答。

《柯林斯英汉双解大词典》

youdao

So far we do not know how much of a problem it might be.

到目前为止，我们还不知道这个问题的严重性。

youdao

The jester said, "If these wise men do not know how to hide the moon, then the moon cannot be hidden."

VOA: special.2009.03.28

What I just spent many lectures discussing is the fact that we can not know how far away an electron is from the nucleus, so we can't actually know the radius of a certain atom.

我花了这么多课时所讨论的正是我们,不可能知道电子离原子核有多远这一事实，因此我们不可能知道某个原子的半径。

麻省理工公开课 - 化学原理课程节选

and they do not know how to fix the tire.

而车上的人对此束手无策。

I can 课堂 - SpeakingMax英语口语达人

It was as if the animals did not know how to cope with their new found freedom.

BBC: Lab chimps successfully treated with anti-depressants

The details will have to be negotiated with Congress, so we do not know how it all works.

NPR: Listeners' Money Questions Answered

They may not know how to price others in the pipeline either, like Facebook.

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