用所给词的适当形式填空，并翻译。

1 you always _ __ (go ) to bed late .
you should _______ (go ) to bed earlier.
2 what should we ________ (do) in class ?
we should ____ (be) quiet in class .
3 jim often ____(help)_____(he) mum ______(clean)the house .
4 we mustn,t ______(spit) on the ground .
look ! that man _____(spit) on the ground.
5 the sing say :" no _____ (smoke)."

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always go 常态
should go should后跟动词原形

do 理由同上
be 同上

helps, his often也虚祥表常态
clean help sb. do sth.

spit must后跟动词原形
spitting 瞧，那人正在往薯旦地上吐痰，用正在进行时

smoking 不准吸烟
no 后面数誉扰跟sth / doing sth

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