Read the situations. Use past modals to complete the possible reasons for the situations.
1. Your roommate overslept and missed an important meeting at work.
He / She could . . .
He / She might . . .
2. Your best friend hasn't called you in a week.
He / She may . . .
He / She couldn't . . .
3. Your grandparents forgot your birthday.
They may not . . .
They might . . .
4. Your sister can't find her favorite earrings.
She must . . .
She could . . .
Check that you use:
• must / could / may / might + have + past participle to speculate about the past
• must have + past participle when you feel 100% certain about your guess
• could have, may have, and might have + past participle when you feel less than 100% certain about your guess
• may / might not have + past participle when you feel it's possible that something didn't happen
• couldn't have + past participle when you feel very certain that something is impossible
Type your answer in the box below and then submit it. Go to the next screen to see the sample answer(s).