Read the Learn this! box. Match the modal verbs from exercise 2 with the rules. (Đọc phần Learn this! Nối các động từ khiếm khuyết ở bài 2 với các quy tắc.)

LEARN THIS! Modals in the past

a. We use may (not) / might (not) / could have + past participle to speculate about the past. We don’t use couldn’t have + past participle in this way.

She might have been worried about something.

b. We use should / shouldn’t have + past participle or ought (not) to have + past participle to say what the right or wrong way to behave was.

He shouldn’t have left early. He ought to have stayed.

c. We sometimes use an exclamation with might have + past participle or could have + past participle (but not may have + past participle or negative forms) to tell somebody how we think they should have behaved.

You might have offered me a biscuit! I was starving!

d. We use must have + past participle and can’t / couldn’t have + past participle to make logical deductions about the past.

They can’t have known about the meeting.

They must have misunderstood your email.

e. We use should have + past participle and was supposed to + infinitive to talk about things we expect to have happened.

She left an hour ago, so she should have reached the airport by now.

She was supposed to take the tickets with her.