“Go under the knife”的意思可不是“在刀的下面走”，理解错就尴尬了！

Go under the knife: 

做手术

例句：

I have to go under the knife next week.  

下周我得去做手术。

On a knife edge：

In a difficult or worrying situation of which the result is very uncertain

处于摇摆不定的处境/令人焦虑的状态；结果未明；形势尚不明朗

例句： 

He is on a knife edge about the coming press conference.  

他对即将召开的记者招待会感到十分焦虑不安。

Twist the knife:

落井下石

例句： 

Don't twist the knife.

不要落井下石。