Rewrite the underline parts of sentences to correct the mistakes.

1. You don't have to smoke here! Look at the sign.
2. You needn't to leave the classroom during the exam.
3. We have to cook dinner tonight because we are going to a restaurant.
4. There is no school tomorrow so I can't get up early.
5. We can chew gum in the classroom because it's impolite.
6. She doesn't need to go out on Saturday evening because she is too young.
7. She mustn't do the shopping today because her husband has already done it.