Modals: Deduction

What is the structure that we use for deductions in the past in the affirmative?

• must + had + past participle

• must + verb in the infitive

• must + have + past participle

• should + have + past participle

The thief ___________ a key. The door was locked and nothing was broken.

• should have

• must have had

• must have

• can't have had

You ______ be serious! Did you really say that to her? You're nuts!

• mustn't

• couldn't

• can't

• have to

They _____ live here. Their car is parked outside the house!

• can't

• should

• shouldn't

• must

Look at his smile! He __________ the exam.

• must have passed

• can't have passed

• should pass

• must pass

They __________ to school this morining because they live 50 miles away.

• must have walked

• must walk

• can't walk

• can't have walked

What is the structure for deduction in the past in the negative?

• must + infinitive

• can't + have + 3rd column (perfect infinitive)

• must + have + 3rd column (perfect infinitive)

• can't + infinitive

She __________very hard because she always gets really bad marks.

• can't study

• can't have studied

• should have studied

• mustn't study

An earthquake? That ____________ terrifying at the moment!

• must be

• must have been

• can't be

• can have been

We don't know for sure if Alex broke the lamp. It ____________ the dog.

• must be

• can't have been

• might have been

• can't be