1: 1. a 3. b 5. b
2: a. may = must, c. didn`t can - couldn`t
3: 1. why did you have to buy do many chairs 3. she doesn`t have to correct my mistakes 5. she shouldn`t go outside today without an umbrella 7. my son mustn`t play with a lighter. 9. you aren`t allowed to shout in museum
4: 1. You must give up smoking. 3. Do you want some more tea? 5. I would like to go with you. 7. You can do whatever you want.