Bài 6: Choose the correct answer in the bracket.
1. There are plenty of potatoes in the fridge. You (can't/needn't) buy any.
2. It's a hospital. You (don't have to/mustn't) smoke.
3. He had been working for more than 11 hours. He (must/ need) be tired after such hard work
4. The teacher said we (can/ must) read this book for our own pleasure as it is optional.
5. If you want to learn to speak English fluently, you (must/need) to work hard.
6. Take an umbrella. It (should/might) rain later.
7. You (shouldn't/ needn't) leave small objects lying around. Such objects (must/may) be swallowed by children.
8. People (mustn't/ needn't) walk on grass.
9. Drivers (must/ can) stop when the traffic lights are red.
10. (May/ Should) I ask a question? Yes, of course.