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III. Underline the correct answer.

1. Please be quiet! This is a library. You must/ mustn't/ don't have to talk loudly.
2. Drivers must/ mustn't/ don't have to stop their cars when the traffic lights turn red.
3. I must/ mustn't/ don't have to ride a bike to school. I can walk there in just ten minutes.
4. I have an extremely important test tomorrow. I have to/ has to/ must study hard for it.
5. We must/ mustn't/ don't have to use mobile phones or make lots of noise in the cinema.
6. When you’re in Australia and New Zealand, you must/ don't have to/ has to drive on the left side of the road.
7. Griffin mustn't/ don't have to/ doesn't have to take a train to Ha Noi. He can take a plane instead.
8. Ms. Beatrice's doctor says that she doesn't have to/ have to/ has to exercise regularly to stay healthy.
9. We have to/ don't have to/ must get up early on Sundays. We don't have classes on Sundays.
10. There is a ‘No Eating or Drinking’ sign by the door. They have to/ don't have to/ mustn't eat or drink here.