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问题 选择题

在等差数列{an} 中，若a4+a6+a8+a10+a12=120，则3a9-a11 的值为（　　）

A．42

B．45

C．48

D．51

答案

∵等差数列{an} 

∴a4+a6+a8+a10+a12=（a4+a12）+（a6+a10）+a8=5a8=120，解得a8=24．

∴3a9-a11=3（a1+8d）-（a1+10d）=2（a1+7d）=2a8=48．

故选C．

单项选择题 B型题

非处方药的批发企业必具有（）

A.《药品经营企业许可证》

B.《药品生产企业许可证》

C.《医疗机构制剂许可证》

D.《营业执照》

E.新药证书
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单项选择题

Many theories concerning the causes of juvenile delinquency(crimes committed by young people) focus either on the individual or on society as the major contributing influence. Theories (91) on the individual suggest that children engage in criminal behavior (92) they were not sufficiently penalized for previous misdeeds or that they have learned criminal behavior through (93) with others. Theories focusing on the role of society suggest that children commit crimes in (94) to their failure to rise above their socioeconomic status, (95) as a rejection of middle, class values.
Most theories of juvenile delinquency have focused on children from disadvantaged families, (96) the fact that children from wealthy homes also commit crimes. The latter may commit crimes (97) lack of adequate parental control. All theories, however, are tentative and are (98) to criticism.
Changes in the social structure may indirectly (99) juvenile crime rates. For example, changes in the economy that (100) to fewer job opportunities for youth and rising unemployment (101) make gainful employment increasingly difficult to obtain. The resulting discontent may in (102) lead more youths into criminal behavior.
Families have also (103) changes these years. More families consist of one-parent households or two working parents; (104) , children are likely to have less supervision at home (105) was common in the traditional family (106) . This lack of parental supervision is thought to be an influence on juvenile crime rates. Other (107) causes of offensive acts include frustration or failure in school, the increased (108) of drugs and alcohol, and the growing (109) of child abuse and child neglect. All these conditions tend to increase the probability of a child committing a criminal act, (110) a direct causal relationship has not yet been established.

A．interaction

B．assimilation

C．cooperation

D．consultation
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