--- You may refuse my invitation , but you must explain why .
--- Oh, I must , _____ ?
| A．did I | B．didn’t I | C．must I | D．mustn’t I |
His failure in the experiment suggested that he _______ his teacher’s proper instructions.
| A．should not have followed | B．should not follow |
| C．mustn’t have followed | D．hadn’t followed |
— The woman biologist stayed in Africa studying wild animals for 13 years before she returned.
— Oh, dear ! She ______ a lot of difficulties !
| A．may go through | B．might go through |
| C．ought to have gone through | D．must have gone through |
The World Wide Web is sometimes jokingly called the World Wide Wait because it ______ be very slow.
| A．should | B．must | C．will | D．can |
— Shall I give you a ride as you live so far away ?
— Thank you. _______.
| A．It couldn’t be better | B．Of course you can |
| C．If you like | D．It’s up to you |
— Lucy doesn’t mind lending you her dictionary.
— She _______. I’ve already borrowed one.
| A．can’t | B．mustn’t | C．needn’t | D．shouldn’t |