21．It was not until dark ____ he found ____ he thought was the correct way to slove the problem.
| A．when; what | B．that; that | C．that; what | D．when; that |
— Must he come to sign this paper himself?
— Yes, he __________.
| A．need | B．must |
| C．may | D．will |
If it were not for the fact that she __________ sing, I would invite her to the party.
| A．couldn’t | B．shouldn’t |
| C．can’t | D．might not |
— What’s the name?
— Khulaifi. __________ I spell that for you?
| A．Shall | B．Would |
| C．Can | D．Might |
— I think I’ll give Bob a ring.
— You __________. You haven’t been in touch with him for ages.
| A．will | B．may |
| C．have to | D．should |
We __________ have proved great adventurers, but we have done the greatest march ever made in the past ten years.
| A．needn’t | B．may not |
| C．shouldn’t | D．mustn’t |