With the development of industry and extension of railroad network in the early 20th century in the U.S.A., there appeared ______.

With the development of industry and extension of railroad network in the early 20th century in the U.S.A., there appeared ______.

A.a rapid growth of cities

B.an influx of foreign goods

C.an increase of urban ghettos

D.a great increase in the number of farms

正确答案是A