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Grammar: modals

Possibility: may/ could/ might (have done)

could/ may/ might to say that something is possibly true now:

The Earth may not be the only planet with intelligent life.

could/ may/ might to say there is a chance something will happen in the future:

We could make contact with aliens in the near future.

may not and might not/ mightnt to say that something is possibly not true now orin the future:

People may (not) have been telling the truth about seeing flying saucers.

could/ may/ might + have + past participle to say that a past event possibly

happened:

Aliens might have visited Earth in the past.

could/ might (but not may) + have + past participle to say that a past event was

possible but didnt happen:

Could aliens have built the pyramids?

Assumption/ deduction: must/ cant (have done)

must to express certainty about the present in the affirmative:

There must be life on other planets.

cant (not mustnt) to express certainty about the present in the negative:

Aliens cant be trying to contact us. Weve received no signals from them so far

must have + past participle to express certainty about the past in the affirmative:

Fossils show that primitive forms of life on Earth must have evolved billions of years ago.

cant have/ couldnt have + past participle to express certainty about the past in

the negative:

Aliens cant have visited Earth because space travel takes too long.

Criticism: should/ ought (not) to/ could + have + past participle

Match the two halves of the sentences!

1. The Egyptian pharaohs were buried in rich tombs. Not all of these have been discovered,

2. Its hard to believe that a structure as complex as a pyramid

3. If humans built the pyramids,

4. The workmen who built them may have believed

5. Many of those workmen6. Some people believe that the pyramids

7. They are convinced that extra-terrestrials

8. They think this alien civilisation

a. they must have been highly skilled craftsmen.

b. couldnt have been built with the technology available then.

c. could have been wiped out by a natural disaster.

d. so more treasures could be lying buried in the sand.

e must have landed on Earth and built them.

f. must have been injured in the course of their work.

g. could have been built in the lifetime of one pharaoh.h. that they were ensuring their own afterlife by building the pyramids.

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Now complete this dialogue using modal verbs from the grammar file and the verbs in brackets.

A: Hey, stop the car! Theres a huge animal in that field. It looks like a puma!

B: Dont be ridiculous. I cant see anything. You .. see) a puma anyway- they arent found

in Britain. It (be) something else.

A: Well, it (be) a puma exactly bit it was definitely some kind of big cat.

B: Lets get out and have a look. I dont suppose it .. (go) far.

A: OK. It was over by that rock.

B: Wow, I can see it! Its huge- it .. (weigh) as much as a big dog!

A: Whats that beside it? Ugh! It.(kill) a sheep or something!

B: Yes, but I wonder where it came from.

A: it..(escape) from a zoo?

B: What zoo? Were miles from anywhere!

A: What shall we do? If we tell the police, theyll say we(imagine) it!