Modal Verbs to Express Certainty and Possibility

Deborah is looking a bit tired. Perhaps she's working too hard. She ______________ be working too hard.

• could

• might

• may

• could have

Ryan is behaving very strangely. I'm sure he's in love. He _____ be in love.

• must

• may

• could

He never goes on holiday. I don't suppose he earns much. He _____ earn very much.

• can't

• couldn't

• may not

• might not

She's studying full-time and has a weekend job at a restaurant. I imagine that's very hard. That __________ be very hard.

• can

• must

• can't

• might

That man is quite young. He's definitely not Claire's grandfather. That ______ be Claire's grandfather.

• can

• must

• can't

He's bought a new car and a yacht. He obviously sold his business for a lot of money. He _______ sold his business for a lot of money.

• must have

• could have

• might have

Andy and Sarah aren't speaking to each other. I don't believe they've had another argument. They _______ another argument.

• can't have

• can't have had

• must have

You seem very familiar. Perhaps we've met before. We _____ have met before.

• may

• might

• could

• must

She says she doesn't like children. I'm sure she didn't have a happy childhood herself. She _____ have had a happy childhood.

• can't

• couldn't

• must

• may not

I don't know why she didn't tell me she'd left her job. It's possible she thought I would be angry. She _____ have thought I'd be angry.

• may

• might

• can

• could