1
It can be used instead of "can not have
2
used to form conditional sentences in English
3
Using this modal also expresses uncertainty.
4
It is used to express a logical conclusion about something that happened in the past.
5
They are used to express possibility in the past. The use of these two manners also expresses uncertainty.
6
It is used in a similar "must have" manner , but in a negative way.
