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。