Complete the sentences using can (cant), could (couldnt) or be (not) able to

EXERCISE 1:Complete the sentences using can (cant), could (couldnt) or be (not) able to. Use can, could if possible; otherwise use be able to.
1. Im sorry I _________ come to your party next week.
2. When Bob was 16, he __could__ run 100 meters in 11 seconds.
3. I havent _________ sleep very well recently.
4. The computer went wrong, but luckily Emma _could_ put it right again.
5. Nicole __can’t___ drive, but she doesnt have a car.
6. Ask Catherine about your problem. She might ______ to help you.
7. As soon as I walked into the room, I __could__ smell gas.
8. Mrs Carter ________ put out the fire before the house burnt down.
9. I used to ________ stand on my head, but I ________ do it any more.
10. Nico got a job as a translator because he ________ speak Chinese.
11. A girl fell into the river, but fortunately we ________ rescue her.
12. Wheres Martin? ~ He ________ be in the garden. Im not sure.
13. Lilian ________ know how to ride a horse; she is too young.
14. Matthew will ________ go to the sea tomorrow. He’s finished all his work.
15. I looked everywhere for the book, but I ________ find it.