Passage 2  Los Angeles in 1947 was not a pleasing backwater like Miami or San Diego. The yearsII had made the city become one of the nation's industrial powerhouses. It may have been known to the restof the country mainly for its film studios in Hollywood and the San Fernando Valley, but the entertainmentindustry, however large its influence on the culture may have been, was only the tip of a huge and verydifferent economic iceberg. Los Angeles may not have looked like Detroit, but it was just as much builtaround manufacturing. Movie stars weren't the typical Angelenos； machine workers in aircraft assemblylines were. The core of the Los Angeles economy was in defense contracting. The city's benign climate and itslarge harbor to the south in San Pcdro, not to mention its presence on the Pacific Rim, had made LosAngeles home to much of the U.S. aircraft industry, with Lockheed, Douglas, Northrop, and Vultee itspillars. Federal dollars poured in during the war years: between 1942 and 1945, 479 new defense plants werebuilt in the area, and hundreds more were expanded. The Defense Plant Corporation, a federal agencycharged with overseeing the use of government funds to build facilities for private contractors, investedmore than $450 million in building or expanding industrial facilities in the Los Angeles area during the waryears. Employment in the region stood at 15,930 in 1938, before the war began； by 1941, spurred bymanufacturing orders from overseas, it had already grown to 120,000. It would expand to employ more than228,000 people just a few years later, at the peak of the war efiort. The shipbuilding industry, almostinconscquential before the war, grew to become the region's second-largest economic force. Localshipyards had not constructed a major vessel for two decades preceding World War II； by the end of 1941,the California Shipbuilding Corporation, known as Calship, had become the nation's most productiveshipyard, delivering 111 shijps for the Defense Department in 1942. Calship employed 55,000 workers, andthe rest of the shipbuilding industry in the region employed another 35,000.
【題組】31. What is the main idea of this passage?
(A) Los Angeles' diverse economic sectors
(B) How World War I! led to a boom in Los Angeles' manufacturing economy
(C) How Los Angeles became famous for its entertainanent industry
(D) Why shipbuilding was important for the US in World War II