Most theories of juvenile delinquency have focused on children from disadvantaged families, (26) ____ the fact that children from wealthy homes also commit crimes. The latter may commit crimes (27) ____ lack of adequate parental control. All theories, however, are tentative and are (28) ____ to criticism.

　　Changes in the social structure may indirectly (29) ____ juvenile crime rates. For example, changes in the economy that (30) ____ to fewer job opportunities for youth and rising unemployment (31) ____ make gainful employment increasingly difficult to obtain. The resulting discontent may in (32) ____ lead more youths into criminal behavior.

　　Families have also (33) ____ changes these years. More families consist of one parent households or two working parents; (34) ____, children are likely to have less supervision at home (35) ____ was common in the traditional family (36) ____. This lack of parental supervision is thought to be an influence on juvenile crime rates. Other (37) ____ causes of offensive acts include frustration or failure in school, the increased (38) ____ of drugs and alcohol, and the growing (39) ____ of child abuse and child neglect. All these conditions tend to increase the probability of a child committing a criminal act, (40) ____ a direct causal relationship has not yet been established.

　　21.[A] acting 　[B] relying 　[C] centering 　[D] cementing

　　22. [A] before  [B] unless   [C] until   [D] because

　　23. [A] interactions 　[B] assimilation

　　    [C] cooperation    [D] consultation

　　24. [A] return 　[B] reply  [C] reference  [D] response

　　25. [A] or  [B] but rather  [C] but  [D] or else

　　26.[A] considering  [B] ignoring [C] highlighting  [D] discarding

　　27. [A] on   [B] in   [C] for  [D] with

　　28. [A] immune  [B] resistant  [C] sensitive  [D] subject

　　29. [A] affect  [B] reduce  [C] chock  [D] reflect

　　30. [A] point  [B] lead  [C] come  [D] amount

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

　　32. [A] case  [B] short 　[C] turn  [D] essence

　　33. [A] survived  [B] noticed  [C] undertaken [D] experienced

　　34. [A] contrarily  [B] consequently

        [C] similarly   [D] simultaneously

　　35. [A] than   [B] that 　[C] which   [D] as

　　36. [A] system  [B] structure [C] concept [D] heritage

　　37. [A] assessable  [B] identifiable [C] negligible [D] incredible

　　38. [A] expense  [B] restriction [C] allocation [D] availability

　　39. [A] incidence [B] awareness [C] exposure [D] popularity

　　40. [A] provided [B] since [C] although [D] supposing