Brian is a 15 year old boy who been skipping class at least once a week for the majority of the past school year and has stayed out all night on several occasions in the past six months. He was recently brought home by the police after being caught hanging out in the park during school hours, drinking beer and smoking cigarettes. He has been associating with “troubled” kids, who are known to vandalize buildings with graffiti, and routinely lies to his parent about where he is going and what he is doing. He has become more aggressive recently and has gotten into a number of physical fights. One of these was at school, resulting in suspension. Based on this brief description, Brian would most likely be diagnosed with: