30．The extra room________very useful when we had visitors．
| A．had been proved | B．was proved |
| C．had proved | D．Proved |
So far this year we ______ a fall in house prices by between 5 and 10 percent.
| A．saw | B．see | C．had seen | D．have seen |
Little Tom admitted ______ in the examination, ______ that he wouldn’t do that in the future.
| A．to cheat; to promise |
| B．cheating; promised |
| C．having cheated; promising |
| D．to have cheated; promised |
World Wildlife Fund ______ very much the efforts that China has made to protect endangered species from being further endangered.
| A．enjoys | B．appreciates | C．thanks | D．prefers |
It’s wise to forget things which aren't worth ______.
| A．being remembered | B．remembering | C．to be remembered | D．to remember |
With the fast development of computer and Internet technologies, traditional printed books ______ by the growing popularity of online reading of e-books.
| A．are challenged | B．have challenged |
| C．are being challenged | D．have been challenged |