Mustn't or don't have to? Underline the correct verb form.

1) You mustn't/don't have to tell Tom what I told you. It's a secret.
2) The museum is free. You mustn't/don't have to pay to get in.
3) Children mustn't/don't have to tell lies.
4) You mustn't/don't have to play with matches. They're dangerous.
5) This is my favorite pen. You can borrow it, but you mustn't/don't have to lose it.