“Must” has no past form, so we generally use the past form of “to have to” to refer to past obligations or strong necessities.
Let’s take a look at some examples, shall we?
She had to leave early because she had an appointment.
Steve had to come with me to work as his car broke down.
I had to study for 3 months to pass this exam.
If we want to make a sentence negative, we do not change the modal “to have to”, we simply add the auxiliary verb “didn’t or did not” in order to show that something was not necessary in the past. The rule applies for all personal pronouns.
Mike didn’t have to bring any food since there was a lot already.
I didn’t have to show my passport when flying from France to Spain.
Sandra didn’t have to buy a ticket because I got one for her.
Finally, if we wish to make a question, we simply use the auxiliary verb “did” followed by the modal verb “to have to” to form the question:
Did she have to wait very long?
No, I didn’t (short answer).
Did you have to buy a ticket to the show?
Yes, I did have to (for emphasis).
Did David have to work tonight?
No, he didn’t have to work tonight (long answer).
Either response may be used.
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