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用转动小滑板法车削如图3所示的锥齿轮坯，求车削各圆锥面时，小滑板应转动的角度和方向。

答案

参考答案：

车削A面时，逆时针转动的角度

a/2=40°

车削B面时，顺时针转动的角度

a/2=180°-88°-40°=52°

车削C面时，顺时针转动的角度

a/2=90°-43°=47°

答车削A面时，小滑板应逆时针转动40°；车削B面时，小滑板应顺时针转动52°；车削C面时，小滑板应顺时针转动47°。

多项选择题

国防领导体制包括（）。

A.国防领导机构设置

B.职权划分

C.相互关系

D.相关制度
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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.

11（）

A.through

B.across

C.into

D.towards
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