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问题 选择题

下列杠杆，有哪一个与其它三个不属于同一类？（　　）

A．正在撬道钉的道钉撬

B．正在拔铁钉的羊角锤

C．正在起瓶盖的起子

D．正在划水的赛艇的桨

答案

道钉撬、羊角锤、起子都是省力杠杆，而赛艇的浆是费力杠杆．

故选D．

单项选择题

下列条件中，（）使项目在面临不确定性因素的变动时发生亏损的可能性减小。

A．固定成本占总成本的比例大

B．高的盈亏平衡产量

C．低的盈亏平衡单位产品变动成本

D．低的盈亏平衡生产能力利用率
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单项选择题

The effect of the baby boom on the schools helped to make possible a shift in thinking about the role of public education in the 1920’s. In the 1920’s, but especially (1) the Depression of the 1930’s, the United States experienced a (2) birth rate. Then with the prosperity (3) on by the Second World War and the economic boom that followed it, young people married and (4) households earlier and began to (5) larger families than had their (6) during the Depression. Birth rates rose to 102 per thousand in 1946, 106.2 in 1950, and 118 in 1955. (7) economics was probably the most important (8) , it is not the only explanation for the baby boom. The increased value placed (9) the idea of the family also helps to (10) this rise in birth rates. The baby boomers began streaming (11) the first grade by the mid-1940’s and became a (12) by 1950. The public school system suddenly found itself (13) The wartime economy meant that few new schools were buih between 1940 and 1945. (14) , large numbers of teachers left their profession during that period for better-paying jobs elsewhere.

(15) , in the 1950’s, the baby boom hit an antiquated and inadequate school system. Consequently, the custodial rhetoric of the 1930’s no longer made (16) ; keeping youths ages sixteen and older out of the labor market by keeping them in school could no longer be a high (17) for an institution unable to find space and staff to teach younger children. With the baby boom, the focus of educators (18) turned toward the lower grades and back to basic academic skills and (19) . The system no longer had much (20) in offering nontraditional, new, and extra services to older youths.

10（）

A.demonstrate

B.interpret

C.exhibit

D.explain
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