Every possible means ______to prevent the air pollution, but the sky is still not clear.
| A．are being used | B．have been used |
| C．has been used | D．had been used |
_____the soap operas, she got down to finishing her homework.
| A．Watching | B．watch | C．Watched | D．Having watched |
I’m afraid Mr. Harding ______see you now. He’s busy.
| A．can’t | B．mustn’t | C．shouldn’t | D．needn’t |
The old man has four sons, and two _____ turned doctors．
| A．of which | B．of whom | C．of them | D．of that |
—Thank goodness, you are here! What _____ you?
—Traffic jam..
| A．kept | B．is keeping | C．keeps | D．had kept |
_____with so much trouble, we failed to complete the task on time.
| A．Face | B．Facing | C．Faced | D．To face |