3. Logical assumptions and deductions
▪ Must:
▪ is used in affirmative sentences and expresses positive logical beliefs.
▪ To state something about which you are certain that is true.
6. Can’t and couldn’t
▪ Can’t and couldn’t are used in negations and express negative
logical assumptions.That is to say, you use them when you’re certain
that something is not true or real.
Monsters can’t be real!
10. Possibility
▪ Can + present infinitive expresses general possibility, something
theoretically possible.
You can have milk or juice.
11. Possibility
Could / may / might + present infinitive = It is possible/likely,
perhaps…
It is used to show that something is possible in a specific situation.
You should keep that number, it may be useful one day.
12. Possibility
Could / may / might + present infinitive = It is possible/likely,
perhaps…
NOTE: we can use can/could/might in questions, but not MAY.
Do you think you can/could/might give me an answer today?
13. Possibility
▪ Could / might / would + perfect infinitive
It refers to past possibility, something that was possible but didn’t
happen.
You might have changed jobs.
14. They would have been a perfect match, but
something got in their way.
17. Obligation, duty and necessity: must
▪ Must expresses duty, strong obligation to do something, as this
something is essential. It also serves to express moral obligation
coming from the very speaker.
I must explain what happened.
18. Obligation, duty and necessity: have to
▪ Have to expresses strong necessity or obligation. We normally use it
when somebody other than the speaker has decided that something
is necessary.
The landlord said that we have to pay
the rent tomorrow.
20. Must and have to
Do you insist that I…?
▪ Must I stay for the whole
meeting?
Is it necessary for me…?
▪ Do I have to buy a new
phone to replace the old
one?
These two verb
constructions have
different meaning in
questions.
21. Obligation, duty and necessity: should
and ought to
▪ Should and ought to express weak obligation or duty. Also,
advice.These are less emphatic than must, have to.
You should think it twice before you make a final decision.
22. Obligation, duty and necessity: need
▪ Need expresses necessity (it is necessary to).
I need to tidy up my room today.
24. Needn’t / don’t have to / don’t need to
▪ These structures are used with the present infinitive, meaning that
it’s not necessary to do something in the present or future.
You don’t need to drive me home, I’ll take a cab.
26. Didn’t have to / didn’t need to
▪ These two expressions are used when it wasn’t necessary to do
something. We don’t know if it was done or not.
He didn’t have to / didn’t need to buy the
newspaper. (we don’t know if he bought the newspaper or
not.)
27. Needn’t + bare perfect infinitive
▪ It was not necessary to do something but, even so, it was done.
(You brought flowers even though
there’s plenty of them already)
You needn’t have brought
flowers!
29. Mustn’t and can’t
▪ They are used to say that it is forbidden to do something. Either
because it is against the laws, rules, or because you are not allowed
to do it.
You mustn’t / can’t use a dictionary during the
exam.
31. Criticism
▪ Could / should / might / ought to + perfect infinitive are
used to criticise someone’s actions or lack of them in the past = it
would have been better if you had…
You could have been on time for the meeting.
33. Now it’s your turn!
Go to page 156 to complete
exercise 3.
34. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
▪ That can’t have been John you saw
at the match – he’s out of the
country at the moment.
35. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
▪ You needn’t have brought
sandwiches – there’s a perfectly
good cafeteria.
36. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
▪ What a mess you’ve made!You
should have been more careful.
37. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
▪ I don’t know why she didn’t ask me
how to do it – I could have easily
helped her.
38. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
She must have thought you were too
busy – I can’t think of another reason.
39. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
Martin really shouldn’t have
borrowed my tennis racket without
asking first.
40. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
I don’t know why Fiona’s so late; do
you think she might have got lost
coming here?
41. Complete the sentences with the following modal
verbs forms and explain their meanings
Must have
Should have
Might have
Could have
Can’t have
Shouldn’t have
Might not have
Needn’t have
She might not have managed to find
the time to come.You know how
busy she is.