Chọn câu đúng: What is the passage mainly about?

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the answer to each of the questions

In 1900 the United States had only three cities with more than a million residents-New York, Chicago, and Philadelphia. By 1930, it had ten giant metropolises. The newer ones experienced remarkable growth, which reflected basic changes in the economy. The population of Los Angeles (114,000 in 1900) rose spectacularly in the early decades of the twentieth century, increasing a dramatic 1,400 percent from 1900 to 1930. 

A number of circumstances contributed to the meteoric rise of Los Angeles. The agricultural potential of the area was enormous if water for irrigation could be found, and the city founders had the vision and dating to obtain it by constructing a 225-mile aqueduct, completed in 1913, to tap the water of the Owens River. The city had a superb natural harbor, as well as excellent rail connections. The climate made it possible to shoot motion pictures year-round; hence Hollywood. Hollywood not only supplied jobs; it disseminated an image of the good life in Southern California on screens all across the nation. The most important single industry powering the growth of Los Angeles, however, was directly linked to the automobile. The demand for petroleum to fuel gasoline engines led to the opening of the Southern California oil fields, and made Los Angeles North America's greatest refining center. Los Angeles was a product of the auto age in another sense as well: its distinctive spatial organization depended on widespread private ownership of automobiles. Los Angeles was a decentralized metropolis, sprawling across the desert landscape over an area of 400 square miles.

It was a city without a real center. The downtown business district did not grow apace with the city as a whole, and the rapid transit system designed to link the center with outlying areas withered away from disuse. Approximately 800,000 cars were registered in Los Angeles County in 1930, one per 2.7 residents. Some visitors from the east coast were dismayed at the endless urban sprawl and dismissed Los Angeles as a mere collection of suburbs in search of a city. But the freedom and mobility of a city built on wheels attracted floods of migrants to the city. 

What is the passage mainly about? 

• A. The growth of cities in the United States in the early 1900's
• B. The development of the Southern California oil fields 
• C. Factors contributing to the growth of Los Angeles
• D. Industry and city planning in Los Angeles