3 Read the sentences and choose the option, a or b, which has the same meaning.
1 My little brother mustn't walk to school on his own. He's only six years old.
b He is not allowed to walk to school on his own.
2 We don't have to finish our English project tonight.
a It is not necessary to finish the project tonight, but you can if you want to.
3 You mustn't eat food during the lesson.
b You are not allowed to eat food during the lesson.
4 I have to study tonight because we have an important history test tomorrow.
b I must study tonight.