This document provides examples of how to use perfect modal verbs - must have, can't/couldn't have, and might have - followed by a past participle to make deductions about past events. It includes examples rewritten with these perfect modal constructions and exercises for the student to practice rewriting sentences in the same way. The key provides the answers to the exercises.

1. B1 Basic – Perfect Modals – Deduction- Rewrite
PERFECT MODALS: LOST
 MUST HAVE + PAST PARTICIPLE
Ethan must have been on the plane.
I am sure he was on the plane.
The Others must have seen the crash.
It is certain that the Others saw the crash.
Jack must have worked as a doctor.
I’m sure that he worked as a doctor.
Claire must have felt bad.
I am positive that she felt bad.
 CAN’T/COULDN’T HAVE + PAST PARTICIPLE
Charlie can’t/couldn’t have rescued the baby.
I am sure that he didn’t rescue the baby.
Kate can’t/couldn’t have seen Walt’s mother.
I am sure that Kate didn’t see Walt’s mother.
She can’t/couldn’t have warned him about it.
I am certain that she didn’t warn him about it.
 MIGHT HAVE + PAST PARTICIPLE
The Others might have heard you.
It’s possible that the Others heard you.
Sawyer might have stolen the guns.
Perhaps Sawyer has stolen the guns.
Shannon might have been in love with Sayid.
It’s possible that Shannon was in love with Sayid.
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2. B1 Basic – Perfect Modals – Deduction- Rewrite
A. Rewrite the sentences:
1. I am sure Hurley left his books at home.
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2. It is certain that Claire didn’t notice the traffic lights.
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3. Maybe Jack forgot to lock the door.
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4. Jin-Soo played in the rain. It was harmful to his health.
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5. Juliet didn’t feel sleepy.
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6. I am sure that Kate was a film star.
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7. Ben didn’t brush his teeth after dinner.
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8. Desmond didn’t see a doctor when he was ill.
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9. It’s certain that Dharma heard of the air crash.
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10. I’m sure that they weren’t on the island.
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11. Maybe Sayid didn’t have an opportunity to find fruit.
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12. I’m certain that Sawyer was behind the tree.
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13. I’m certain that Sun broke your glasses by accident.
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14. I couldn’t find Charlie. It is possible that he is lost.
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B. Rewrite the sentences with MIGHT HAVE or MUST HAVE + PAST PARTICIPLE
1. Perhaps she’s broken her leg. ________________________________________
2. The exam was very easy. I’m sure I’ve passed._______________________________
3. Eko hasn’t come. I’m sure he’s forgotten.__________________________________
4. Perhaps I’ve lost my keys.___________________________________________
5. Perhaps Libby has gone back home.____________________________________
6. The boat isn’t there. I’m sure the Others have taken it. _______________________
7. Perhaps Ana-Lucia’s great-grandfather was a soldier.______________________
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3. B1 Basic – Perfect Modals – Deduction- Rewrite
Answer Key:
A: Rewrite the sentences:
1. Hurley must have left her books at home.
2. Claire can’t have noticed the traffic lights.
3. Jack may/might/could have forgotten to lock the door.
4. Jin-Soo shouldn’t have played in the rain.
5. Juliet must have slept well.
6. Kate must have been a film star.
7. Ben should have brushed his teeth.
8. Desmond should have seen a doctor when he was ill.
9. Dharma must have heard of the air crash.
10. They can’t have been on the island.
11. Sayid may/might not have had an opportunity to find fruit. (NOT “could”)
12. Sawyer must have been behind the tree.
13. Sun must have broken your glasses by accident.
14. He may/might/could have got lost. (He might be lost)
B: Rewrite the sentences:
1. She may/might/could have broken her leg.
2. I must have passed the exam.
3. Eko must have forgotten the meeting.
4. I may/might/could have lost my keys.
5. Libby may/might/could have gone back home.
6. The Others must have taken the boat.
7. Ana-Lucia’s great-grandfather may/might/could have been a soldier.
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