1. The letter must have already been sent.
2. Mom may have cooked dinner - the smell is so nice!
3. She may have come home and got upset.
4. the ancient people might have lived in the area
5. The rain seems to have stopped.
Вот еще пара на всякий случай:
She expected to have been called.
I hoped to have been helped.
1. I happened to be waiting for the bus at that moment.
2. You must be joking.
3. The film must be ending now.
4. The child may be falling asleep.
5. The house must be being built.