Telepathy
Your bestie always phones you on your birthday. Yesterday was your birthday but she didn’t phone you. (She must have...//She could have...)
She must have lost my phone number // She could have decided to break off our friendship
You are usually at the top of the class for spelling in your English lessons, but the teacher tells you that all your answers are incorrect. You don’t believe it. (I can't have... // The teacher must have...)
I can't have made a mistake // The teacher must have misunderstood something.
Your cousin told you she was going to marry a Hollywood actor. (She might have... // She can't have...)
She might have gone crazy // She can't have met any Hollywood star.