听力原文： It may seem strange to date the emergence of a global economy in 1973, since that was the year of the first oil shock. The price of a barrel of oil was raised dramatically, leading to a slump in the economics of industrialized nations. Yet, by 1973 the world economy had leveled. The United States had ceased to be the dominant player it had been in the decade immediately after World War Ⅱ. Western Europe and Japan had rebuilt and were providing serious competition to the United States in international trade. New stars were emerging in the Far East: Taiwan and Hong Kong regions of China, South Korea, Singapore, to name a few. And by the 1990s, Thailand, Malaysia, Indonesia, and South China were in hot pursuit. But more than competition was at stake. A truly international financial system existed, based on computer technology and instant communication. Money traveled the globe at the speed of light, as much as a trillion dollars each day, to be invested wherever it was needed. Transnational corporations placed manufacturing and service operations wherever it made the most sense to do so. Manufacturing plants went to countries with large labor forces willing to work for much less than workers in more developed nations. Japanese companies overcame trade barriers in the United States by building manufacturing plants there. Corporations in other countries imitated this tactic. Simultaneously, large regional trading blocs were emerging, beginning with the European Communities. Canada and the United States signed a free-trade agreement, which was later expanded to include Mexico in one large free-trade bloc. A similar trend was evident in East Asia. Which was the major cause of the emergence of the global economy in 1973?