Among the problems is _____ they often failed to take into account that those people are more likely to use sunscreen.
| A．that | B．what | C．when | D．where |
He paid for a seat, when he ______ have entered free.
| A．could | B．would | C．must | D．need |
Helen ______ go on the trip with us, but she isn’t quite sure yet.
| A．shall | B．must | C．may | D．can |
— Tom is never late for work. Why is he absent today ?
— Something _______ to him.
| A．must happen | B．should have happened |
| C．could have happened | D．must have happened |
If I ________ plan to do anything I wanted to. I’d like to go to Tibet and travel through as much of it as possible.
| A．would | B．could | C．had to | D．ought to |
— Do you know where David is ? I couldn’t find him anywhere.
— Well. He ______ have gone far –his coat’s still here.
| A．shouldn’t | B．mustn’t | C．can’t | D．wouldn’t |