Fill in the gaps with correct modal: can, can't, might, could, couldn't, must. mustn't, don't , have to.

1) John doesn't need a calculator . He ___ do sums in his head

2) I ___ swim well when I was a child. I even won the school championships

3) It ___ rain today. It's getting cloudy already

4) I ___ pay for the tickets because I got them from Sam for free.

5) That was excellent work. But I ___ do it without you

6) "Children, you ___ cross the street if the lights are red!"

7) You ___ be 18 to see that film

8) I ___ find my keys. I probably left them at my mother's place

9) Dad ___ go and see a doctor. His cough is getting worse all the time​