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 (51) on the individual suggest that children engage in criminal behavior (52) they were not sufficiently penalized for previous misdeeds or that they have learned criminal behavior through (53) with others. Theories focusing on the role of society suggest that children commit crimes in response to their failure to rise above their socioeconomic status, (54) as a rejection of middle-class values. Most theories of juvenile delinquency have focused on children from disadvantaged families, ignoring the fact that children from wealthy homes also commit crimes. The latter may commit crimes (55) lack of adequate parental control. All theories, however, are tentative and are (56) to criticism. Changes in the social structure may indirectly (57) juvenile crime rates. For example, changes in the economy that lead to fewer job opportunities for youth and rising unemployment (58) make gainful employment increasingly difficult to obtain. The resulting discontent may in turn lead more youths into criminal behavior. Families have also (59) changes these years. More families consist of one-parent households or two working parents; consequently, children are likely to have less supervision at home (60) was common in the traditional family structure. This lack of parental supervision is thought to be an influence on juvenile crime rates.
52().
A.before
B.unless
C.until
D.because
参考答案：D
解析：
A．before：“在……之前”，引导时间状语从句。B．unless：“除非”，引导条件状语从句，[例]My baby sister never cries unless she is hungry．我刚出生的妹妹除非饿了，她是从来不哭的。C．until是“直到……”，引导时间状语从句，[例]We can’t start the job until we have the approval from the authority concerned．没有有关当局的批准我们不能开始这项工作。D．because：conj/adv．因为，在本题中为正确答案，引导原因状语从句，解释前面“engage”的原因。