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问题 选择题
现有四所大学进行自主招生，同时向一所高中的已获省级竞赛一等奖的甲、乙、丙、丁四位学生发出录取通知书．若这四名学生都愿意进这四所大学的任意一所就读，则仅有两名学生被录取到同一所大学的概率为（　　）
A．
1
2
B．
9
16
C．
11
16
D．
7
24
答案

由题意知本题是一个古典概型，

试验发生包含的所有等可能的结果相当于甲、乙、丙、丁四位学生任选四所大学之一，共有44种，

满足条件的事件是仅有两名学生被录取到同一所大学，

可先把四个同学分成1+1+2三份，有C42种分法，

再选择三所大学就读，即有C42A43种就读方式．

∴所求的概率为

C24
A34
44
=
9
16
．

故选B．

单项选择题

肠溶衣

A．丙烯酸树脂Ⅱ号
B．羟丙基甲基纤维素
C．虫胶
D．滑石粉
E．川蜡
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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.

3（）

A.took

B.produced

C.brought

D.carried
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