36.There have been__________ periods in the development of American political parties in

 the United States.

A. two                                                           B. three

C. four                                                          D. five

37.The 1920s in the United States has been described by many historians as a period of

___________.

A. material failure                                           B. spiritual frustration

C. political setbacks                                        D. welfare reform

38.___________is the largest single source of goods imported by the U.S.，accounting for nearly

30％of the total.

A. Canada                                                      B. Mexico

C. Japan                                                        D. European Union

39.Mark Twain’s masterwork was ___________ .

A. The Scarlet Letter                                       B. Leaves of Grass

C. The Sketch Book                                        D. The Adventures of Huckleberry Finn

40.In the early part of the 19th century，___________was the center of American writing.

A. Boston                                                      B. Philadelphia

C. Chicago                                                     D. New York City