---We've spent too much money recently.
---Well，it isn't surprising. Our friends and relatives ______ around all the time.
A．are coming B．had come C．were coming D．have been coming
At the eve of Christmas, she got nothing but $ 2 ____ to buy her husband a simple present.
A．with what B．which C．what D．with which
_____ private cars bring us convenience, they also cause more traffic accidents and pollution.
A．While B．As C．If D．Since
______ around the Water Cube , we were taken to see the Bird’s Nest for the 2008 Olympic Games.
A．Having shown B．To be shown C．Having been shown D．To show
Her book didn’t ____ children probably because she employed too many scientific terms.
A．appeal to B．apply for C．intend for D．refer to
After years of research, he found the key ____ differences between species.
A．to explain B．to explaining C．of explaining D．explaining
