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问题 单项选择题

原料油与焦化干气混合制氢，焦化干气烯烃含量高，造成加氢反应器床层温度高，应（）

A、降油量、提焦化干气量

B、提油量、降焦化干气量

C、降油量、降焦化干气量

D、提油量、提焦化干气量

答案

参考答案：B

填空题

想一想，填一填．

（1）42÷7=6，______和______是______的因数．

______是______和______的倍数．

（2）按要求在□里填上合适的数字．

使47□是偶数，□里可以填上：______

使75□是3的倍数，□里可以填上：______

使5□是质数，□里可以填上：______

使47+5□的和是偶数，□里可以填上：______．
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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.

9（）

A.at

B.on

C.for

D.with
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