A great many cities are experiencing difficulties which are nothing new in the history of cities, except in their scale. Some cities have lost their original purpose and have not found new one. And any large or rich city is __1__going to attract poor immigrants, who flood in, filling with hopes of __2__prosperity which are then often disappointing. There are backward towns on the edge of Bombay or Brasilia, just as though there were on the edge of __3__seventeenth-century London or early nineteenth-century Paris. This is new is __4__the scale. Descriptions written by eighteenth-century travelers of the poor of Mexico City, and the enormous contrasts that was to be found there, are very __5__dissimilar to descriptions of Mexico City today—the poor can still be numbered __6__in millions.The whole monstrous growth rests on economic prosperity, but behind it lies __7__two myths; the myth of the city as a promised land, that attracts immigrants __8__from rural poverty and brings it flooding into city centers, and the myth of the __9__country as a Garden of Eden, which, a few generations late, sends them flood __10__-ing out again to the suburbs.

答案：

1 在new one前加a.这里one指代上下文中的可数名词purpose，因此该词前要有限定词。

2 将filling改为filled.在这里，非谓语动词fill与句子的who(poor immigrants)之间是逻辑动宾关系，因此要使用过去分词来表示被动意义。

3 去掉though.

4 将this改为what.根据句子结构，我们可以看出这里需要一个关系代词，它既能引导主语从句，同时也可以在从句中作主语，这个关系代词就是what。如：What I like in a good author is not what he says，but what he whispers。

5 将was改为were.that引导定语从句，其先行词是descriptions…and the enormous contrasts,因此谓语动词be要用复数。

6 将dissimilar 改为 similar.这里要表示的是“共同，相似”之处。

7将lies 改为lie.behind it lie two myths 是个倒装句，主语为two myths，可见谓语动词要使用复数。

8 将that改为which.这里是一个非限制性定语从句，因此不可用that，而要用which。

9 将it改为them.复数名词immigrants的代词，所以要用复数形式。

10 将late改为later