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 13. Sam really ___ to pay more attention during lessons. 
a)ought b)should c)might
14. You ___ expect me to know everything!
a)have to b)can't c)must
15. You ___ to use your mobile phone on an aeroplane.
a)aren't allowed b)can't c)don't have
16. Let's ask Eleanor - she ___ know.
a)can b)shouldn't c)might
17. I ___ see you later if I finish work on time.
a)can't b)might c)must
18. He ___ to get there before we do.
a) is bound b)must c)is able
19. ___ attend the meeting?
a) Must I b)Do I have to c)Am I
20. You ___ pay for the hotel room. Your company has already paid.
a)can't b)don't have to c)mustn't

13.c)

14.c)

15.a)

16.c)

17.b)

18.b)

19.b)

20.a)

13. c14. a15. a16, a17, c18,  b19. b20. c