Unit 12
Hard Work
Grammar
Modal Verbs of Deduction
1. Must/can’t/might be (Present)
2. Must/can’t/ might + have + Past participle (Past)
Modal Verbs of Deduction
We can use modal verbs for deduction – guessing if something is true using the
available information (evidence) . The modal verb we choose shows how certain we are
about the possibility.
1- [ Present ] Modal Verbs of Deduction
Deduction
sure to happen
positive deductions.
possible/perhaps
sure not to happen
negative deductions
Present
must be
must+inf. [without to]
might be
might+inf.
can’t be
[without to]
Example
My friend won the gold
medal. He must be happy
now
Sara is absent. She might
be ill; I’m not sure
He always does his work
seriously. He can’t be
careless
After may, might, must or can’t we can use be + -ing, when we are talking about actions in progress.
• They’ve gone to Ibiza, and right now they must be having a great time.
• Call him. He might be waiting for us.
Modal Verbs of Deduction
 What deduction can you make about this picture :
must
It is sure….
may / might.
It is Possible…..
Can’t
It’s impossible….
+infinitive
(without to)
Or
be + v + ing
2- [ Past ] Modal Verbs of Deduction
Deduction
sure to happen
positive deductions
possible/perhaps
sure not to happen
negative deductions
must have + p.p.
might have + p.p.
can’t have + p.p.
Past
Example
John’s car is not here. They’re looking under the
He must have gone
table and all around.
out
They might have lost
something
It can’t have been easy to
move to another place.
She liked her village very
much
 Common errors
Correct
Incorrect
Ali can’t be sad. He Ali mustn’t be sad.
has won a gold medal. He has won a gold
medal.
Explanation
In deduction, the
negative form of
must be is can’t be.
 these verbs, like all modal verbs, are followed by an infinitive without to.
Modal Verbs of Deduction
 What deduction can you make about this picture ?
must
It is sure….
May / might.
It is Possible…..
Can’t
It’s impossible….
have
P.P.
Practice
 Choose the correct answer.
1 - Ahmed has a souvenir of the Eiffel Tower. He (must – might) have been to Paris.
Perhaps he spent a holiday there.
2 - They (must - can’t) have won the match, they didn’t score any goal.
3 - He (must - can’t) be a clever mechanic. He always repairs our cars well.
4 - Leila felt ill after she ate at the restaurant yesterday. The food (can’t - must) have
been bad.
5 - Sami (mustn’t - can’t) have travelled to Alexandria yesterday. He was in Cairo.
6 - Mariam has lived in London for 20 years. She (must - can’t) speak English well.
7 - I (might - must) spend the weekend in my village. I haven’t decided yet.
Answer key
1 – Might
2 - can’t
3 - must
4 - must
5 - can’t
6 - must
7 - might