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》

When people began sailing out of sight of land, sailors did not know how to tell where they were on the open sea.

VOA: special.2010.07.14

I filled this room with expensive scientific equipment that I did not know how to use.

VOA: special.2011.06.18

It was a place where people owned things that they did not know how to use.

VOA: special.2010.01.03

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

Wal-Mart security officers were also present overnight, but he said he did not know how many.

CNN: Wal-Mart worker dies in rush; two killed at toy store

But Lischer said he did not know how many agents hand the brochures out.

FORBES: Knowledge @Wharton