31. If I _________ under the ladder to catch you when you fell, you _____now.
| A．hadn’t stood ; wouldn’t be smiling | B．hadn’t stood , couldn’t have smiled |
| C．didn’t stand, won’t be smiling | D．didn’t stand, couldn’t be smiling |
Up to now, our society ________ with limited living space and a shortage of natural resources.
| A．has been challenged | B．is being challenged |
| C．is challenging | D．has challenged |
—Will you see me off at the airport at ten tomorrow morning?
—Sorry, I ________ a lecture then.
| A．will be giving | B．will give |
| C．give | D．have given |
—The rain ________ fast and heavy.
—You should ________ some shelter. Look at you—you are all wet.
| A．is coming; find | B．comes; have found |
| C．came; find | D．came; have found |
I had wanted to help you last night but I couldn't spare any time, for I ________ a composition which I have to hand in this morning.
| A．wrote | B．was writing |
| C．had written | D．have written |
—How is your cousin, Kate?
—She broke her leg and ________ medical treatment since.
| A．is receiving | B．has received |
| C．received | D．has been receiving |