题目内容：
3[填空题,20分] International trade-the exchange of goods and services 1 borders is often explained by the theory of comparative advantage which has become the cornerstone of modern thinking 2 international trade. This theory was produced by David Ricardo 3 was an English economist in the nineteenth century. This theory points out that trade between countries can be 4 beneficial even if a country is less 5 than another in the production of every commodity. As 6 as there are minor, relative differences in the efficiency of producing a commodity, 7 the poor country can have a comparative advantage in producing 8 comparative advantage is not a static concept. A country may 9 a particular comparative advantage purely through its own actions, independent of the endowments of nature. A case in point is Switzerland’s 10 advantage in watchmakin
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