I'm sure Jane is sleeping now.(PRESENT)
Jane must be sleeping now.
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. (SPECULATION)
He may / might come to the party.
Perhaps he left the car unlocked.(PAST)
He might / could / may have left the car unlocked.
I'm sure you didn't ferget doing your homework.
You can't have forgotten doing your homework.
I'm sure they aren't at work today. (DEDUCTION)
They can't be at work today.
Did you hear me come in last night? No, I (be) -----asleep. (DEDUCTION)
must have been
Kate is shivering. She ------------- be cold. (DEDUCTION)
must
It is impossible that he is Spanish. (DEDUCTION)
He can't be spanish.
Emily is crying. She --------------- be sad.
must
I had an umbrella when I came out but I haven't got it now. You (leave) ------------- it on the bus.(SPECULATION)
might / could / may have left
I'm sure she is at home today.(PRESENT)
She must be at home today.