People have become aware ______the fact that carbon dioxide, poison to the environment, contributes_____ air pollution.
| A．of, to | B．/, to | C．of, of | D．of, for |
— I'm leaving tomorrow.
— Oh, what a pity! I won't be able to see you off. I __ a tele-conference the whole morning.
| A．have | B．am having | C．will be having | D．will have had |
__ is not possible that Bob can win the first prize in the competition.
| A．This | B．That | C．It | D．What |
— How come you are here?
— I came here for nothing else but to see you ____.
| A．by chance | B．in addition | C．at random | D．on purpose |
I didn't see your sister at the party. If she __, she would have met my brother.
| A．has come | B．had come | C．did come | D．came |
— Oh, my cat is really fat.
— You __ have given her so much food.
| A．wouldn't | B．mustn't | C．couldn't | D．shouldn't |