Past modals of deduction: what must have happened here? Past modal exercises for guessing what happened

This B2 drill lesson gives past modals of deduction exercises, using clues you see now to say what must, might or can't have happened.

Grammar: Must have for sure, might / may / could have for maybe, might not have for maybe not, can't / couldn't have for impossible, questions with could, and have been + -ing.
Topic: Archaeology: field notes from Corrow Bend, an invented dig, with the director's blog, a museum label for a clay horse and a chat with Cressida, a volunteer.
Activities: Sorting by certainty, choices, verb gaps, tables, matching, word order, find-the-mistake quizzes, drag-and-drop texts, two memory games, an anagram, a chat and a test.

What's inside

Chapter 1The rule
- PictureUnlock
- Study the scheme: past modals of deductionGrammar schemeTry it
- Is the sentence correct? Mark true or falseTrue or falseUnlock
- Sort the sentences: how sure is the speaker?Sort into columnsTry it
- Choose the right formChoose the optionUnlock
- Fill in the gaps: the missing wordFill in the gapsUnlock
Chapter 2Sure or maybe? must have, might have
- Find the matching pairs: verb and past participleMemory gameUnlock
- Fill in the gaps: must have + past participleFill in the gapsTry it
- Choose the right words: sure or maybe?Choose the optionUnlock
- Fill in the gaps with might, may or could have: maybe it happenedFill in the gapsUnlock
- Match the clues and the explanationsMatchUnlock
- Put the words in the right order: must have and might haveUnjumbleUnlock
- Read Nadezhda's message and drag the words into the gapsDrag and dropUnlock
Chapter 3No way or maybe not? can't have, might not have
- Choose the right words: impossible or maybe not?Choose the optionTry it
- Fill in the gaps with can't have or couldn't have: it's impossibleFill in the gapsUnlock
- Fill in the table with past modals: sure, maybe not or impossible?Fill in the tableUnlock
- Find the mistake and choose the right words: negatives and questionsQuizUnlock
- Put the words in the right order: negatives and questionsUnjumbleUnlock
- Match the sentences and the reasonsMatchUnlock
- Read Ebba's email and drag the words into the gapsDrag and dropUnlock
Chapter 4Trickier cases: been + -ing, now or then, had to
- Fill in the gaps: modal + have been + -ingFill in the gapsUnlock
- Choose the right form: now or in the past?Choose the optionUnlock
- Choose the right words: a guess or something necessary?Choose the optionUnlock
- Choose the right sentence for the situationQuizUnlock
- Put the words in the right order: been + -ingUnjumbleUnlock
- Read Hyacinth's post and drag the words into the gapsDrag and dropTry it
- Find the mistake and choose the right words: mixedQuizUnlock
Chapter 5Real life: Secrets of Corrow Bend
- Read the field notes from the digReal-life documentUnlock
- Read the field notes again: true or false?True or falseUnlock
- Read the dig blog and fill in the gaps with past modals: sure, maybe or impossible?Fill in the gapsUnlock
- Read the museum label and drag the words into the gapsDrag and dropUnlock
- Choose the right replies: Cressida texts youChatTry it
- Test yourself: choose the right answerQuizUnlock
Chapter 6Homework
- Choose the right form: guesses about the pastChoose the optionUnlock
- Fill in the gaps: modal + have + past participleFill in the gapsUnlock
- Fill in the gaps with past modals: sure, maybe or impossible?Fill in the gapsUnlock
- Put the words in the right order: guesses about the pastUnjumbleUnlock
- Fill in the table: now and in the pastFill in the tableUnlock
- Sort the sentences: correct or wrong?Sort into columnsUnlock
- Match the situations and the guessesMatchUnlock
- Find the matching pairs: more past participlesMemory gameUnlock
- Unscramble the past participlesAnagramUnlock
- Find the mistake and choose the right words: everyday guessesQuizUnlock
- Choose the right sentence: how sure can you be?QuizUnlock
- Choose the right words: guess, necessity, now or then?Choose the optionUnlock
- Fill in the gaps with modal + have been + -ing: what were they doing?Fill in the gapsUnlock
- Read Thorvald's blog post and fill in the gaps with past modals: who emptied the bird feeder?Fill in the gapsUnlock
- Read Vesna's email and drag the words into the gapsDrag and dropUnlock

Grammar: past modals of deduction: must have, might have, can't have

When you see a result now and work out what happened before, use a modal + have + past participle: The streets are white. It must have snowed in the night. The choice of modal shows how sure you are, from must have to might have to can't have.

Past modals of deduction: what must have happened?

Look at what you see now and guess what happened before: modal + have + past participle.

Modal + have + past participle

The pattern is the same with every modal: Ana might have missed the bus. Leo can't have cooked this. Write have, not has or had, and gone, not went. In speech it sounds like must've, but it is never written must of.

modal + have + past participle

subjectmust / might / may / could / can't / couldn'thavepast participle

The streets are white. It must have snowed in the night.

Ana is late. She might have missed the bus.

Leo can't have cooked this. He can't even boil an egg.

have never changes · no can have

have never changes, and the verb after it is a past participle: She might have (not has) gone (not went). Never use can have for maybe: He might have (not can have) missed the train. In speech, have sounds like 've (must've, might've), but never write must of.

Sure, maybe, maybe not or impossible?

Must have: I'm sure it happened. Might, may or could have: maybe. Might not or may not have: maybe not. Can't or couldn't have: impossible. In American English, must not have can also mean you're sure it didn't happen: He must not have heard the phone.

How sure are you?

How sure?	Form	Example
I'm sure it happened.	must have + past participle	The car is clean. Dad must have washed it.
Maybe it happened.	might / may / could have + past participle	I can't find my keys. I may have left them at work.
Maybe it didn't happen.	might not / may not have + past participle	The plants look dry. Tom might not have watered them.
I'm sure it didn't happen. It's impossible.	can't / couldn't have + past participle	Max couldn't have taken the car. He can't drive.
Question	Could + subject + have + past participle?	Could she have forgotten? · What could have happened?
In progress at that moment	modal + have been + -ing	Nobody answered. They must have been working in the garden.

can't have, must not have, might not have

can't have and couldn't have mean the same: I'm sure it didn't happen. In American English, must not have can mean that too: He must not have heard the phone. might not have and may not have are only a maybe: She might not have seen your message (but maybe she did).

Questions and have been + -ing

Questions put could first: Could the bus have left early? For an action in progress at that moment, use have been + -ing: I didn't hear the phone. I must have been taking a shower.

Someone must have moved my chair.I'm sure
The museum may have closed early today.maybe
You can't have met Ben at the party. He was in Rome.impossible
Ellie might not have read your email.maybe not
Could the bus have left early?a question
I didn't hear the phone. I must have been taking a shower.in progress at that moment

Now or then? Must have or had to?

A guess about now takes a base form: She must be at home now. About the past, add have: She must have been at home last night. Had to says something was necessary: The elevator was broken, so we had to take the stairs.

Now or in the past?

Now: modal + verb

She must be at home now. Her car is outside.
He can't be hungry. He's just had lunch.
They might be asleep at the moment.

Past: modal + have + past participle

She must have been at home last night. Her lights were on.
He can't have been hungry. He'd just had lunch.
They might have been asleep when you called.

must have or had to?

must have + past participle is a guess about the past: There's smoke in the kitchen. Dad must have burned the toast. had to + verb says that something was necessary: The elevator was broken, so we had to take the stairs. A guess → must have. Something necessary → had to.

Common mistakes

Watch for He must had forgotten, She can't have went home and They might has missed the train. And a maybe is never can have: He might have lost his phone, not He can have lost his phone.

He must had forgotten my birthday.
He must have forgotten my birthday.
modal + have, never had
She can't have went home yet.
She can't have gone home yet.
have + past participle: go → gone
They might has missed the train.
They might have missed the train.
have never changes
He can have lost his phone.
He might have lost his phone.
maybe → might / may / could have

More lessons on this grammar: Modal verbs lessons and exercises

Try the past modals of deduction exercises

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What's in the lesson

38 auto-checked exercises
7 games
1 real-life document
1 grammar scheme
1 picture

The main objectives of this lesson are to:

say you're sure it happened with must have + past participle: The whole pie is gone! The kids must have eaten it.
say maybe with might, may or could have, and maybe not with might not have: He might not have read my message yet.
rule something out with can't or couldn't have: Tom couldn't have broken the window. He was at school all day.
use have been + -ing for an action in progress: You didn't answer my call last night. You must have been sleeping.
keep a guess apart from a necessity: The dog must have dug it, but The trains weren't running, so we had to walk home.

Grammar:: past modals of deduction · must have · might have / may have / could have · can't have / couldn't have · modal + have been + -ing
Topic:: grammar practice · archaeology · mysteries and explanations · history

Teaching tips

Set up a scene before class: leave an empty cup, an open umbrella and a half-eaten sandwich on a desk; groups explain what must, might or can't have happened there.
Move guesses from now to last night: say a guess about the present (She must be at home), and students shift it into the past: She must have been at home last night.
Explain the dig before the blog: after the field notes, pairs explain the ash, the seashell and the 1987 coin in their own words, then fill in the director's blog.

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The whole course: English Grammar Practice · B2

English Grammar Practice · B2 has 24 drill lessons, one grammar point each: the future perfect and continuous, the third and mixed conditionals, wishes, past modals, the impersonal passive, have something done, participle clauses, reporting verbs and verb patterns. Each has the rule as a scheme, 43 to 47 exercises that check themselves, 15 of them for homework, and no new words.See the course

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