1.a) heights b )flying c)spiders d)the dark e)germs
2.a) sounds b)smells c)looks d)tastes e)feels
3.a) can't b)mustn't c)don't have d) have to e)can
4.a) couldn't b) couldn't c)had to d)didn't have to e)couldn't
5.a)can't b)might c)must d)can't e)might
6.a) must b)can't c)might d)must e)might