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     1    on the individual suggest that children engage in criminal behavior     2    they were not sufficiently penalized for previous misdeeds or that they have learned criminal behavior through     3    with others. Theories focusing on the role of society suggest that children commit crimes in     4    to their failure to rise above their socioeconomic status,     5    as a rejection of middle-class values.
    Most theories of juvenile delinquency have focused on children from disadvantaged families,     6    the fact that children from wealthy homes also commit crimes. The latter may commit crimes     7    lack of adequate parental control. All theories, however, are tentative and are     8    to criticism.
    Changes in the social structure may indirectly     9    juvenile crime rates. For example, changes in the economy that     10    to fewer job opportunities for youth and rising unemployment     11    make gainful employment increasingly difficult to obtain. The resulting discontent may in     12    lead more youths into criminal behavior.
    Families have also     13    changes these years. More families consist of one-parent households or two working parents;     14    , children are likely to have less supervision at home     15    was common in the traditional family     16    . This lack of parental supervision is thought to be an influence on juvenile crime rates. Other     17    causes of offensive acts include frustration or failure in school, the increased     18    of drugs and alcohol, and the growing     19    of child abuse and child neglect. All these conditions tend to increase the probability of a child committing a criminal act,     20    a direct causal relationship has not yet been established. 
 
【正确答案】 C
【答案解析】 动词短语辨析。act(on)“对……起作用”;rely(on)“依靠,指望”;center(on)“以……为中心,围绕”;commenting(on)“对……做出评论”。空格处填入的分词应和前一句中的concerning、后一句中的focusing on相呼应,都表示“关于……的理论”的含义。分析上下文可知,这里指关注个人因素和社会因素的两种理论。所填词与on搭配后应与第三句中的focusing on同义,故答案为C。