I'm sure you didn't forget about your homework. (PAST)
You can't have forgotten about your homework.
Did you hear me come in last night? No, I ____ ____ ____ (BE) asleep.
must have been
Perhaps he left the car unlocked. (PAST)
He might/could/may have left the car unlocked.
I'm sure Jane is sleeping now. (PRESENT)
Jane must be sleeping now.
I'm sure they aren't at work today. (PRESENT)
They can't be at work today.
I had an umbrella when I came out but I haven't got it now. I _____ ____ ____ (LEAVE) it on the bus, but I'm not sure.
might/could/may have left
I'm sure she is at home today. (PRESENT)
She must be at home today.
It is possible that you forgot your wallet at home. (PAST)
You might/could/may have forgotten your wallet at home.
John will probably come to the party. (PRESENT)
He may/might/could come to the party.
Emily is crying because her doll has broken. She ____ be sad. (PRESENT)
must
It is impossible that he is 65 years old. (PRESENT)
He can't be 65 years old.
Kate is shivering. She ____ be cold. (PRESENT)
must