搜题请搜索小程序“爱下问搜题”
问题 不定项选择

下列关于位移和路程的说法中，正确的是 [ ]

A．位移大小和路程不一定相等，所以位移与路程不相同

B．位移的大小等于路程，方向由起点指向终点

C．位移描述物体位置的变化，路程描述路径的长短

D．位移描述直线运动，路程描述曲线运动

答案

答案：C

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.

12().

A. creek

B. flood

C. bonus

D. pledge
查看答案
单项选择题

鼻中隔动脉的分布中没有下列哪项（）

A.筛前动脉

B.筛后动脉

C.内眦动脉

D.鼻腭动脉

E.颈内动脉的分支
查看答案