31. ________was difficult to save 
the places and buildings _____destroying their old beauty.
| A．That…unless | B．This…except | C．It…without | D．There … except for |
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 |
In many people’s opinion, that company, though relatively small, is pleasant ______.
| A．dealt with | B．dealing with | C．to be dealt with | D．to deal with |
The computer system _____suddenly while he was surfing the Internet.
| A．broke up | B．broke out | C．broke in | D．broke down |
It is usually warm in my hometown in March, but it _____ be rather cold sometime.
| A．must | B．can | C．should | D．would |