1) You must know the law to not to go to prison
2) "Push the button! You must do it!" - she said to her companion.
3) You mustn't give your address to people whom you don't know well.
4) He mustn't cheat or he we'll be disqualified.
5) My classmate can't play games until he does his homework.
6) "He couldn't fail! It can't be truth!" - Mary shouted.