We often do certain things because they are necessary. Have to or has to is used to express necessity and obligation. To express necessity or obligation in the past, we use had to.
(a) Aunt Polly was angry, but she ……… laugh.
(b) I do not like to punish him but I will …………………. punish him for stealing the jam.
(c) Tom ………………….. drink the pain killer.
(d) A farmer ………………… work hard in his fields.
(e) I ……………….. cash a cheque.
(f) She …………………… stay at home and help her mother.
