To speculate about something in the past we use can’t/must + have + past participle.Įxample: Max’s father must have worked very hard. ( but not: Max’s grandfather can be retired.) We use m ust to express something we are 100% sure is true in the present.Įxample: Max’s grandfather must be retired, he’s 90 years old.
We use can’t to express something we are sure is untrue or impossible in the present.Įxample: Max can’t be retired, he’s 12 years old.Example: Max’s grandfather may/might have wanted to retire when he was 50. To speculate about something in the past we use may/might (not) + have + past participle. We can replace may/might with could in positive sentences, but not with can.Įxample: Max’s father may/might/could retire soon, he is almost 60. We use may/might when we think something is perhaps true, but we are not 100% sure.Įxample: Max may/might not want to work in the garage forever.
