1. I've seen him wearing his coat.
COMPARE THE SENTENCES
MUST
MUST HAVE
Do you know where Tom is?
Do you know where Tom is?
I need to talk to him.
I can't see him anywhere.
must have
Oh, he left.
Well, it's 8 o'clock.
He be at home.
must
I've seen him wearing his coat.

2. - He MUST be at home. - He MUST HAVE left. Must + base form
certainty that something is true
- He MUST be at home.
Must have + Past participle
certainty or logical conclusion about a past action
- He MUST HAVE left.

3. COMPARE should/ought to Why didn't she invite me to the party?
You read
your s.
They could contact you
should/ought to have
You read
sooner than you expect
your s.
She invited everyone
last week

4. You SHOULD/OUGHT TO read your e-mails
advice/
suggestion
Should/Ought to + base form
Something you should do
You SHOULD/OUGHT TO read your s
Should have/Ought to have + past participle
a criticism or regret
about a past event
Something you should have done
but you didn't
You SHOULD/OUGHT TO HAVE read your s

5. COMPARE You tell him. shouldn't You told him. shouldn't have
He could get angry.
He is angry now.
SHOULDN'T HAVE + PAST PARTICIPLE
SHOULDN'T + BASE FORM
CRITICISM OR REGRET
ADVICE
ABOUT A PAST EVENT
Something you shouldn't have done
Something you shouldn't do
but you did

6. COMPARE Why is she so late? How will she get here?
I don't know, actually.
She taken
may/might have
She take the bus.
may/might
the wrong bus

7. She MAY/MIGHT take the bus
base form
May/Might +
a guess about the future,
a possibility in the future
She MAY/MIGHT take the bus
May have/Might have+ past participle
a guess about a past action,
a possibility in the past
She MAY/MIGHT HAVE taken the wrong bus

8. COMPARE thing to do. Be careful! It was a stupid You hurt yourself
could
thing to do.
You hurt yourself
could have

9. You COULD hurt yourself
Could + base form
Possibility that something could happen, could be done
You COULD hurt yourself
Could have + past participle
Possibility that something could have happened, but it didn't happen
Possibility that something could have been done, but it wasn't done
You COULD HAVE hurt yourself

10. Would have + past participle
I called him, but I
would have
didn't have my mobile
Would have + past participle
Something I would have liked to do
but I didn't because of something
not depending on my willingness