Modal verbs

1.You _______ tell anyone what I just told you. It’s a secret.

a. Don’t/don’t have to
b. Mustn’t
c. Shouldn’t

2. Children _______ obey their parents.
a. Have to
b. Should
c. Ought to

3. You __________ wear uniform in class.
a. need to
b. should
c. have to