This document discusses the multiple uses of modal verbs to express probability and obligation in both past and present contexts. It provides examples of modal verbs like "must", "could", "should" used to show varying degrees of certainty or possibility about past actions, as well as modal verbs like "have to", "had better", and "should" used to express opinions or advice about past and present situations.

1. MODALS with MULTIPLE USES

2. To show that something was probable in the past:
VERY CERTAIN
 must (not) have V3
 can’t have V3
 couldn’t have V3

3. Jack had a stomachache after dinner.
Sofia was at a movie with me last night.
He must have eaten too much.
You couldn’t have seen her at the mall.

4. To show that something was possible in the past:
UNCERTAIN
 could have V3
 may (not) have V3
 might (not) have V3

5. He could/may/might have missed the bus this morning.
Tanya was supposed to meet me before school.
David is usually here by now.
She may/might not have gotten the message.

6. PAST
 must (not) V1
 have to V1
 have got to V1
 had better (not) V1
 should (not) V1
OPINION or ADVICE
PRESENT
 should (not) have V3

7. Parents have got to monitor the shows
their children watch.
The kids have better not spend
so much time indoors playing
computer games.

8. I should have listened the advice
my parents gave me
about having a healhty life.
We should not have ignored the scientists’
warnings about global warming.

9. THANKS 
thechadash

10. THANKS 
thechadash