He did not know how he ought to behave.

他不知道自己应该怎样表现。

《牛津词典》

Her grief was still raw and he did not know how to help her.

她的悲伤仍然强烈直露，他不知道如何帮助她好。

《柯林斯英汉双解大词典》

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》

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.

FORBES: Groupon Soars Afterhours -- It's China and Mobile Businesses Rocket