WHAT CAN MODAL VERBS OF PROBABILITY EXPRESS? OR BEEN USED FOR?

MUST

CAN'T

We don't have all the facts so we're not absolutely sure, but we're pretty certain.

May/Might/Could
express probability in present or future
+Negative (couldn't is not so common)

Continous infinitive is formed with BE + ING.

Asking

Probability in past

Perfect infinitive

How to express degrees of posibility in past

continuous infinitive