The key ingredient in adolescent drug use and other forms of delinquent behaviour is

A) the influence of the mass media.
B) socioeconomic status.
C) family structure.
D) peer involvement.

Peer involvement has been consistently identified as the most significant factor in adolescent drug use and delinquent behavior. Adolescents are more likely to engage in these behaviors if their peers do. Peer pressure can override individual values and beliefs, and influence adolescents to make choices that they wouldn't make on their own. Other factors such as family structure and socioeconomic status may also play a role but are not as significant as peer involvement. Mass media can also contribute to drug use and delinquent behavior, but it is not the key ingredient.