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 ________on the individual suggest that children engage in criminal behavior ________they were not sufficiently penalized for previous misdeeds or that they have learned criminal behavior through ________with others. Theories focusing on the role of society suggest that children commit crimes in ________ to their failure to rise above their socioeconomic status, ________ as a rejection of middle-class values. Most theories of juvenile delinquency have focused on children from disadvantaged families, ________ the fact that children from wealthy homes also commit crimes. The latter may commit crimes ________ lack of adequate parental control. All theories, however, are tentative and are ________ to criticism. Changes in the social structure may indirecfiy ________ juvenile crime rates. For example, changes in the economy that ________ to fewer job opportunities for youth and rising unemployment ________ make gainful employment increasingly difficult to obtain. The resulting discontent may in ________ lead more youths into criminal behavior. Families have also ________ changes these years. More families consist of one-parent households or two working parents; ________ , children are likely to have less supervision at home ________ was common in the traditional family ________ This lack of parental supervision is thought to be an influence on juvenile crime rates. Other ________ causes of offensive acts include frustration or failure in school, the increased ________ of drugs and alcohol, and the growing ________ of child abuse and child neglect. All these conditions tend to increase the probability of a child committing a criminal act, ________ a direct causal relationship has not yet been established.

A．in general
B．on average
C． by contrast
D． at length