If you ___ (not know)the answer,you'd better ____(put)up your hands.怎么写,急

问题描述:

If you ___ (not know)the answer,you'd better ____(put)up your hands.怎么写,急

don't know,put
if主将,从现.you 一般现在时的否定句用:don't + 动词原形
had better do sth.最好做某事,所以用动词原形