The most important features in the growth of the American economy in
the early 20th century were ______.
A. the use of steam and electricity as chief energy, the use of machines and
the development of railway
B. the appearance of airplane, the use of electricity on a large scale and
urbanization
C. the development of large corporation, urbanization and the application in
production of new technology
D. the development of industry and large cities, the expansion of railroad
network
