Where to use "must/should/might/may/could/shouldn't have "in a sentence?
We had in our book that "must+perfect infinitive" is used when we feel sure about sth in the past.And "might/may/could+perfect infinitive" should used when we think sth was possible but we aren't sure.And we should use "should+perfect infinitive" when we talk about past events that did not happen.
Now we had exercises about choosing them.Now I have some question.
1.How can we decide which one is "may/might/could+perfect infinitive" when they are the same?
2.We had an exercise "Nobody answered the phone at the clinic.It................ closed early"
Here the answer written is "must have" instead of being probable we aren't sure then why did we use it?
And also we had "Sarah looks really pleased with herself.She ...............passed her driving test this morning" which gives the answer "must have"but we aren't sure.