【闯关提分训练】must和have to1. Can you go shopping with us this afternoon?Sorry, I cant. I _ look after my little sister.A. can B. may C. have to2. May I smoke here?No, you _. This is a no-smoking room.A. neednt B. mustnt C. need D. wouldnt3. Someone is knocking at the door. It _ be my mother. Its time for her to be back.A. can B. may not C. must D. mustnt4. (2016 江