用may， might， probably， possible，can’t填空。
1. — Listen! Helen is singing in the next room.
— It          be Helen. She has gone to Beijing.
2. He told me that he             be late for school.
3. It’s            for us to finish the task before 7 o’clock.
4. It            rain later. So take an umbrella with you.
5. It will             snow tomorrow， so I will stay at home and read a book.