Помогите с английским

1. Some people just don’t know how to sing (be able to)

2. There's a chance that she's in the airport. (could)

3. I knew how to ride horse when I was six. (could)

4. John isn't sure if he is going to go to Turkey. (might not)

5. Do not block the emergency exit. (mustn't)

6. It is dangerous to use mobile phones on the plane. (mustn't)

7. It is necessary to fasten your seat belt for landing and taking off. (must)

8. It's possible that he'll be there to meet us. (may)

9. This is a surprise. Don't tell anybody about it. (shouldn't)