1: 1;3;52: a;c3: 1;3;5;7;94: 1;3;5;7

1: 1. a 3. b 5. b
2: a. may = must, c. didnt can - couldnt
3: 1. why did you have to buy do many chairs 3. she doesnt have to correct my mistakes 5. she shouldnt go outside today without an umbrella  7. my son mustnt play with a lighter. 9. you arent 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.