I'm sorry, but Samantha is not here. It's 5:00 p.m., so she ___ already left the office. (certainty)
must have
She ___ studied really hard (probability). She passed all her exams with excellent grades.
must have
He ___ known it was your birthday. (certainty) Otherwise, he would have wished you a happy day.
couldn't have
I had to wait 45 minutes for a bus yesterday. There ___ been an accident or a strike. (possibility)
might / may / could have
The boss is in a terrible mood. The meeting ___ been good. (certainty)
couldn't have
You ___ forgotten about the Spanish test, because I'm pretty sure I told you about it. (certainty)
must have
He _________________ arrived by now (probability). It's only a 10-minute journey!
must have
He ___ bought a new car. (certainty) He told me he didn't have any money.
couldn't have
He ___ tried to fix the roof himself. (certainty) Everyone knows that he is a real handyman.
must have
Andrew didn't study for the test, but he's passed. I think he ___ cheated. (possibility)
might / may / could have
I left my bicycle in front of the library, but it's disappeared. Someone ___ stolen it. (certainty)
must have
Sarah ___ been so happy when she found out she won the lottery! (probability)
must have