Section C (12 points)

Directions: Complete the following passage by using ONE word that fits the context.

Shopping habits in the United States have changed greatly in the past few decades.   48    in the 1900s most American towns and cities had a Main Street. Main Street was always in 49 heart of a town. This street was built on both sides with many varied businesses. Here, shoppers walked into stores to look at all sorts of goods. _50__in the 1950s, a change began to take place .Too many automobiles had crowded into Main Street while too__51_­­­­­­­­parking places were available for shoppers. _52__the streets were crowded, merchants began to look with interest at the open spaces from the city limits. Open space is what their car-driving customers needed.

An open space is  53 they got when the first shopping centre was built. Shopping centres, or rather malls, were set __54_ as a collection of small new stores near crowded city centres. Towards the late 1970s,many shopping malls had almost developed into small cities themselves. In addition to providing the cheapness of one stop shopping, malls were transformed into landscaped parks, _55__benches, fountains, and outdoor entertainment.

20世纪80年代以后，水源水中的（）污染成为人类最关注的问题

A.元机物

B.微生物

C.有机物

D.有毒物质