That smart girl studied a lot, so she ***(do) well on the test.
That smart girl studied a lot, so she must have done well on the test.
A: Who broke the big vase in the back office? B: It ***(be) Leo - he's very clumsy. But I'm not sure.
A: Who broke the big vase in the back office? B: It (might/may) have been Leo - he's very clumsy. But I'm not sure.
Scientists claim a giant asteroid hit the Earth in the Gulf of Mexico 65 million years ago and that ***(cause) the extinction of the big dinosaurs.
Scientists claim a giant asteroid hit the Earth in the Gulf of Mexico 65 million years ago and that must have caused the extinction of the big dinosaurs.
The big grammar test is today. I'm in trouble - I ***(study) last night, but I didn't!
The big grammar test is today. I'm in trouble - I should have studied last night, but I didn't!
Taylor Swift's boyfriend just left her for a girl who isn't even famous. She *** (not / be) happy when she found out!
Taylor Swift's boyfriend just left her for a girl who isn't even famous. She (can't/couldn't) have been happy when she found out!
A: Ellen has never missed a day of work before. B: She was coughing yesterday, and she didn't look good. She *** (get) sick.
A: Ellen has never missed a day of work before. B: She was coughing yesterday, and she didn't look good. She must have (got/gotten) sick.
We didn't go to bed early last night. Now we are very tired.
We could have gone to bed earlier last night.
It would have been impossible to finish my homework if my friend didn't help me.
I couldn't have finished my homework without my friend's help.
I am not sure, but it is possible that she forgot about our meeting.
She might have forgotten our meeting.
