Speculate

speculate = to guess about the possible causes or effects of something without

knowing all the facts or details

Speculating about the present

must + infinitive

• It’s 2 pm. Peter hasn’t eaten since 6 am.• What can we deduce?• HUNGRY• He must feel hungry.• We use must because we are sure something

is true.

may / might / could + infinitive

• Mary is absent today.• What can we deduce?• ILL• She may / might / could be ill.• We use may / might / could because maybe it

is true.

may not + infinitive

• I’m not sure whether I can lend you any money.

• What can we deduce?• HAVE ENOUGH• I may not have enough.• We use may not because maybe it is not true.

can’t + infinitive

• He has just eaten 6 hamburgers!• What can we deduce?• HUNGRY• He can’t be hungry.• We use can’t because we are almost sure it is

not true.

Why is the baby crying?

hungry

She must be hungry.

Why is the baby crying?

happy

She can’t be happy.

Why is the baby crying?

spoiled

She may / might / could be spoiled.

Why is the student sleeping in class?

tired

He must be tired.

Why is the student sleeping in class?

the class / boring

The class may / might /could be boring.

Why is the student sleeping in class?

Teresa / his teacher

Teresa can’t be his teacher.

Why are the students so happy?

Teresa / their teacher

Teresa must be their teacher.

Why are the students so happy?

English class now

They may / might /could have English class now.

Why are the students so happy?

a test today

They can’t have a test today.

must/may/might/could/can’t

• Congratulations on passing your exam. You … be very pleased.

• … must …• That woman is asking a lot of questions. She …

be a journalist. Or perhaps she’s a spy.• … may / might / could …

must/may/might/could/can’t

• Relax and do the test. You’re an excellent student. You … fail.

• … can’t …• Where’s Bob? I don’t know. He ... be having lunch.• … may / might / could …• She’s very bad-tempered. She ...have many

friends.• … can’t …

must/might/could/can’t

• A: Do you know where my address book is? B: It ...be in the hall cupboard. I think I saw it

the other day.… may / might / could …• This parcel is making a ticking noise – throw it

out of the window! It ... be a bomb! (September 12th, 2001, in the USA)

• … must …

Speculating about the past

Why are 9th grade students so happy?

They must have done an excellent English test.

They may /might / could have had an English class.

They can’t have done lots of ECA on the weekend.

Speculating about the past

must / may / might / could / can’t+ HAVE

+ PAST PARTICIPLE

Speculate about the past using these verbs:ENJOY LEAVE GO BE SEND

• Henry’s office is locked. He ... home.• ... must have gone ...• I’m not sure but this house ... a school once.• ... might have been ...• Jane is such a nice girl. She ... me this rude e-

mail.• ... can’t have sent ...

Speculate about the past using these verbs:ENJOY LEAVE GO BE SEND

• A: Do you know where my umbrella is? B: No, but you ... it at school. ... may have left ...• I don’t know why you wanted to stay at that

party. You ... talking to all those boring people.• ... can’t have enjoyed ...

Speculate about the past using a SUITABLE verb.

• A: Did you hear the explosion? B: What explosion? A: There was a loud explosion a few minutes

ago. You ... it.... must have heard ...• A: Where is Julia? B: I don’t know. She ... to the toilet.... may have gone ...

Speculate about the past using a SUITABLE verb.

• A: Who was the man we saw with Ann yesterday?

B: I’m not sure. It ... her brother.... might have been ...• You got here very quickly! You ... a taxi.... must have taken ...• It rained every day during their holiday at the

seaside, so they ... a very nice time.... can’t have had ...

Speculate about the past using a SUITABLE verb.

• I wonder why Bob didn’t phone me. He ...... might have forgotten ...• I left my bike outside the house last night and

this morning it isn’t there anymore. Somebody ... it.

... must have stolen ...• I saw some students at the mall, but they

didn’t talk to me. They ... me.... can’t have seen ...