Past Modals for Speculating

A: I fell asleep in the middle of the movie.

B: Wow. You _________ have been really tired.

• couldn't

• must

A: John did very well on the exam.

B: Oh! He _________ have studied very hard.

• could

• must

A: I called you last night, but you didn’t answer.

B: Oh, sorry. I _________ have turned off my phone.

• could

• must

A: Jim isn’t here yet. Did he call you?

B: No, but he _________ have missed his bus. He sometimes does.

• couldn't

• might

A: Where’s Derek? He’s not at his desk.

B: He _________ have gone out for lunch. It’s too early.

• couldn't

• could

A: I hear Jean drove to work today. Did she finally get a car?

B: No, but her father is traveling in Asia, so she __________ have borrowed his.

• couldn't

• might

A: Why wasn’t Kelly at the meeting today?

B: I saw her write it in her calendar, so she ___________ have forgotten.

• couldn't

• might

A: Why did Randy quit his job?

B: I'm not sure. He _________ have gotten a new job.

• might

• must

A: Why hasn't Kate been answering her phone?

B: I don't know. She _________ have been busy.

• must

• might

A: Sandra failed the test.

B: She __________ have studied enough.

• mustn't

• couldn't