hang by a thread/hair

危在旦夕

A:Where are you going?

A:你要去哪儿?

B:I'm going to the hospital.

B:我要去医院。

A:What's the matter?

A:出什么事啦?

B:Professor Wang was hurt in a traffic accident.

B:王教授出车祸了。

A:That's too bad. How are things now?

A:太糟糕了，现在情况怎么样?

B:His life is hanging by a thread, and he is under an emergency treatment.

3：他的生命危在旦夕，正在紧急抢救。