A、At the beginning of the 19th century. B、At the late of the 18th century. C、At the beginning of the 18th century D、In the middl

W：(19) You are an expert on urban problem. Mr. Cross. I wonder how you would describe the characteristics of these enormous cities．
M：The first point to make is that they are different from large cities in Europe and America.
W：Surly all large cities are essentially similar．
M：It’s true that all large cities experience similar problems provisioning housing and services，but the difference lies in the time factor．
W：Surly some of the cities we are considering are just as old and, in some cases，much older, than cities in the United States，for instance.
M：Very true, but the large cities of Europe and the United States grew relatively slowly．(21) London had a population of more than a million at the beginning of the nineteenth century and this number of more than eight million. And this growth was parallel to industrial growth throughout the country．The same is true of New York, for example．
W：But this is not true of Mexico city or Buenos Aires?
M：No，it is not．(20) Throughout Latin America and in parts of Asia, cities have grown much faster than industry，or agriculture for that matter．Some of these cities have quadrupled in size in less than two decades，while industrial growth over the same period may have only reached thirty to forty percent．
W：What does this mean?
M: Essentially the population growth is not equal to the number of employment opportunities. Much of the increase is due to immigration from the countryside, a movement of people in search of better conditions.