21. Supported by the ______ queen, Christopher Columbus discovered the New World in the late 15th century.

　　A. Spanish B. Danish

　　C. Portuguese D. Norwegian

　　22. According to the textbook, there are ______ big cities with a population over two million in the U.S.

　　A. 5 B. 1 5

　　C. 21 D. 30

　　23. The first ______ were brought to North America as slaves in 1619.

　　A. Blacks B. Hispanics

　　C. Indians D. Mexicans

　　24. In September, ______, the Treaty of Paris was signed and Britain recognized the independence of the United States.

　　A. 1776 B. 1781

　　C. 1783 D. 1785

　　25. Black slavery disappeared in the north because of the following EXCEPT that ______.

　　A. the price of slaves was high

　　B. the North disliked black slaves

　　C. the North turned towards industry

　　D. the Africans could not stand cold winters in the North

　　26. ______ was NOT a feature in the growth of the American economy in the early 20th century.

　　A. A mushroom growth of cities

　　B. A slow development of steel industry

　　C. A rapid development of new technology

　　D. A growth of industrial and financial mergers

　　27. The ______ in the U.S. has been described by many historians as a period of material success, spiritual frustration or confusion and purposelessness.

　　A. 1890s B. 1920s

　　C. 1930s D. 1950s

　　28. American policy towards the Soviet Union in the Second World War was centered on the following considerations EXCEPT ______.

　　A. keeping the Soviet Union in the war

　　B.being watchful about Soviet expansive intention

　　C. getting the Soviet Union into the war against Japan

　　D. working out a strategy of alliance with the Soviet Union

　　29. The most important issue in ______ diplomacy after Pearl Harbor was the formulation of a grand strategy of Europe first.

　　A. Soviet-American B. Franco-American

　　C. Sino-American D. Anglo-American

　　30. The idea of containment towards the Soviet Union was first brought up by ______ , a high-ranking official in the American embassy to Moscow.

　　A. Harry Truman B. George Kennan

　　C. George Marshall D. Franklin D. Roosevelt