1. He has to leave at four to catch the train.
a. can
b. must
c. has to
2. We mustn't cross the street now, there is a red light.
a. can't
b. mustn't
c. don't have to
- May I open the window? No, it's very cold in here.
a. must
b. may
c. do... have to?
4. The children mustn't swim here, the river is too deep (глубокий) in this place.
a. can't
b. don't have to
c. mustn't