3. Perhaps it was Helen who rang you up. 4. Possibly they didn't see us in the crowd.
5. Perhaps my parents have gone to the museum.
Exercise 2. Open the brackets using the necessary form of infinitive.
1. She must (to be) mad if she thinks he is going to lend her any more
money.
2. They must (to be) upset when they heard the news.
It's the third time he's been playing the piano today. He must really (to
enjoy it.
Oh, look how white and clean everything is! It must (to snow) at night.
5. You must (to study) English for several years already. Your language is
excellent.
