Modal verbs English - modal auxiliaries

Choose the correct modal auxiliary.

6. I (couldn´t/can´t) play tennis yesterday.

7. She (must/can´t) the Internet. Her parents won´t let her.

8. You (must/mustn´t) cross here. It´s too dangerous.

9. The bell has rung. (May/Needn´t) we go outside?

10. Please take your mobiles, then I (mustn´t/can) call you.