1. SPECULATION & DEDUCTION IN THE PAST
8b lesson - 29th October 20013
SPECULATION & DEDUCTION IN THE PAST

2. To speculate and make deduction in the past we use the following constructions:
MUST - MAY/MIGHT/COULD - CAN'T/COULDN'T + have + past participle
As you know must - may/might/could - can't/couldn't are modal verbs and each of them is used for a specific purpose.

3. must + have + past participle is used to express a certainty that something happened in the past, normally by deduction.
For example: "I must have left my mobile phone in the car. It isn't in the house."

4. may/might/could + have + past participle are used to express deduction about a possibility.
For example: "Pete's late. He could/may/might have missed the bus!"

5. can't/couldn't + have + past participle are used to express past impossibility by deduction.
For example: "You can't/couldn't have lost your keys. You used them to open the door"

6. may have had might have been
Here below you can find a very simple exercise.
Fill in the spaces.
1) David: "Orson walked straight past me and didn't say "hello". And I'm sure he saw me."
June: "He (may/have) something in his mind or he (might/be) in a terrible hurry.”
may have had
might have been

7. must have got
2) The thieves ………. (must/get) into the house through this window. It's broken.

8. couldn’t have made
3) The thieves (couldn't/ make) any noise because the neighbours didn't hear them

9. could have left
You (could/leave) your keys in the kitchen. Look there.

10. can’t have studied
He (can't/study) much for the exam because he failed horribly.