An 8-Year-Old Boy Is Brought to the Physician by His

An 8-year-old boy is brought to the physician by his foster mother because of poor performance at school for the past 8 months. His teachers reported that he does not listen to their instructions, often talks during class, and rarely completes his school assignments. He does not sit in his seat in the classroom and often cuts in line at the cafeteria. His foster mother reports that he runs around a lot inside the house and refuses to help his sister with chores and errands. He frequently interrupts his foster mother's conversations with others and talks excessively. She has found him trying to climb on the roof on multiple occasions. He was placed in foster care because of neglect by his biological parents 3 years ago. Physical examination shows no abnormalities. Neurologic examination shows no focal findings. Which of the following is the most likely explanation for this patient's behavior?

A) Adjustment disorder
B) Attention-deficit hyperactivity disorder
C) Conduct disorder
D) Social anxiety disorder
E) Oppositional defiant disorder