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4.2 can/have to/must (obligation)
Select the sentence which has a different meaning.
1 a) You must do your homework.
b) You have to do your homework.
c) You can do your homework.
2 a) We don't have to go in.
b) We can't go in.
c) We mustn't go in.
3 a) It's not necessary to use a pen.
b) You don't need to use a pen.
c) You mustn't use a pen.​