Consider the following scenario, and then answer the question. Charlie, an 8-year-old boy, comes in with his mother for his first psychotherapy appointment. After meeting with them, you learn that Charlie has a history of fighting and arguing in school and at home. He tends to lose his temper and deliberately refuses to comply with instructions from adults. These behaviors are causing significant difficulties with family, friends, and teachers. As a child psychologist, your first working diagnostic hypothesis would most likely be that Charlie suffers from which of the following?