Page 30 - IELTS Preparation Grammar and Vocab

Modals (1)

2.4 Must, have (got)to: necessity, deduction
We can use either must or have to to say that it is necessary to do something, although have to is less formal and
is also preferred in questions:
The cabin staff must / have to accept the new working conditions if the airline is to compete.
When we say that something was necessary in the past we use had to, not must
Up to 200 teachers and pupils had to be evacuated from a school in South Wales today.
To say something is necessary in the future we use will have to:
To stay in business we will have to cut our costs.
We use must when we decide that, in our opinion, something is necessary or important:
I must give you my email address.
Have to suggests that the necessity comes from outside; for example, from a rule or official order
The council has to close two city centre car parks following a health and safety report.
We usually use must, rather than have to, when we conclude that something (has) happened or that something
is true.
The bridge must have cost a fortune.
When we conclude that something is impossible, we use can't or couldn't
That can't be right, surely? (not Thot-mustk-befightr surely?)
Sometimes we can use either have to or have got to, although have got to is more informal. We use have to with
frequency adverbs and with other modal verbs:
Islanders normally have to queue for half an hour to get on the ferry.
The airlines will have to return to the negotiating table.
If have is contracted (e.g. I've), then we must include got
They've got to be changed. (not Theiive-fe-be-ehangecli)
When we use the past simple we prefer had to rather than had got to:
The manager seemed to be doing a good job. Why did he have to go? (not Whr had-he-get-to-ge?)

1111 Didn't need to, didn't have to, needn't have: 'not necessary'
To say it was not necessary to do something in the past, we use didn't need to or didn't have to:
He didn't have to wait long for a response. (= he didn't actually wait long)
When we think something that was done in the past was not necessary, we use need not (needn't) have
The event organisers expected the bad weather to affect ticket sales. However, they need not have worried, as
every ticket was sold (= they worried but it was not necessary)
2.6 Should, ought to: obligation
We can often use either should or ought to to talk about obligation (in giving advice and recommendations,
saying what we think is a good idea and talking about responsibility):
I think we ought to / should keep Borland for the islanders! (= it's a good idea)
The authorities ought to / should prosecute companies that cause pollution. (= talking about responsibility)
We can use either should or ought to to say that something is likely because we have planned it or expect it
to happen:
They say the road will be ready in five years, but they should / ought to be able to build it faster.
We use shouldn't rather than oughtn't to if something is unlikely:
If you're in the south of the country, you shouldn't be troubled by any rain today.

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