must have could have

Must Might May Could have

Past Possibility or Probability

Must have

Must have (usually pronounced “mustuv”) indicates a highly likely or probable event in the past

(+): Subject + must have + verb-3.
(-): Subject + must not have + verb-3.

● I can’t find my flash disk. —> You must have left it at the office.
● Wai Kwan didn’t come to the party last Thursday. —> She must have been very busy.
● Oliver certainly has a big appetite! —> He must not have eaten all day.

Might have, May have, Could have

May have, might have, and could have expresses a possible event in the past.

(+): Subject + could/may/might + have + verb-3.
(-): Subject + may/might + not have + verb-3.

● Why did Maryam return to Riverton? —> She might have felt disillusioned with LA.
● Clark was fired. —> He may have used company equipment for his own personal use.
● I saw Bigfoot while hiking in the mountains last spring. —> It could have been a bear.
● Bill didn’t get hired. —> He may not have had the right qualifications.

Couldn’t have

Couldn’t have talks about doubt or a highly unlikely or improbable event in the past.

● Tony?!? He couldn’t have scored the highest on the exam!
● Already?!? They couldn’t have finished the assignment so soon.
● We heard Joao in the conference room. —> That couldn’t have been him; he’s on an assignment in the North Sea.

Here are some situations. What are some possible explanations?

Moving, Movements, Migration

1. Gina moved from her native country, Australia, to Ireland.

2. Ernest and his girlfriend have moved into his parents’ home.

3. Roger, a teenager, has run away from home.

4. Bradley has lived in Argentina, Brazil, China, Greece, Italy, Japan, Poland, Russia, Spain, Thailand, Turkey. Now, he plans on moving to Kazakhstan.

5. Susan does not want to return to Nigeria.


6. Clark, an average student, had the highest test score.

7. Rajpal was the valedictorian of his school, and got a scholarship to Harvard University.

8. Jun-seo can speak good Farsi (Persian) and English.

9. Patrick has to repeat another year in school.

Work, Finances

10. Ryan has landed a sinecure job (high-paying job with little responsibilities).

11. Troy is late.

12. Herbert has been fired from his job.


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