1. I don't think they left for Mexico.
They may not have left for Mexico.
2. I'm sure she lost her way.
She must have lost her way.
3. Perhaps he is feeling ill.
He may be feeling ill.
4. I don't think he will be seeing us tomorrow.
He won't be seeing us tomorrow.
5. I'm sure she wasn't at home.
She can't have been at home.
6. Perhaps she lost the way.
She may have lost her way.
