Complete the sentences with must, mustn't or needn't. (Hoàn thành câu với must, mustn't or needn't)
1. You _____ take off your shoes if they are clean.
2. Students _____ turn off their mobiles during lessons or the teacher will take them away.
3. You _____ go to the check-in desk if you have checked in online.
4. In most Arab countries, you _____ eat with your left hand. You should use your right hand.
5. When you're driving, you _____ stop if someone steps onto the pedestrian crossing.
6. We _____ waste any more time.
