Complete the following sentences using an appropriate auxiliary verb form.
1. You have been riding non-stop for hours. You ………………….. be very tired.
a) must
b) can
c) ought
2. She ………………… be about forty.
a) must
b) can
c) will
3. I know I left my phone on this table and it is not here now. Somebody …………………… it.
a) must take
b) must have taken
c) can have taken
4. That ………………… be true. She will never do something like that.
a) can’t
b) shouldn’t
c) shall
5. You ……………………. him a fool. It really upset him.
a) shouldn’t call
b) shouldn’t have called
c) can’t have called
6. The doctor said I ………………. give up smoking.
a) must
b) can
c) ought
7. You …………………… nicer to her. She really cares for you.
a) should have been
b) must have been
c) can have been
8. ……………….. you mind standing up for a moment?
b) Should
b) Would
c) Either could be used here
9. That was a bad place to go hiking. You …………………. your back.
a) could have broken
b) should have broken
c) would have broken
10. ‘Who is at the door?’ ‘It …………………. be the postman.’
a) must
b) could
c) Either could be used here
Answers
1. You have been riding non-stop for hours. You must be very tired.
2. She must be about forty.
3. I know I left my phone on this table and it is not here now. Somebody must have taken it.
4. That can’t be true. She will never do something like that.
5. You shouldn’t have called him a fool. It really upset him.
6. The doctor said I must give up smoking.
7. You should have been nicer to her. She really cares for you.
8. Would you mind standing up for a moment?
9. That was a bad place to go hiking. You could have broken your back.
10. ‘Who is at the door?’ ‘It must / could be the postman.’ (Use must if you are certain that the person at the door is the postman. Use could to express possibility.)
