Trevor spent the first four years of his life living with various family members and in various foster homes. Maggie, his second cousin, adopted Trevor about six months ago. Although she provides him with love, support, and stimulation, Trevor does not seem attached to her. He resists any kind of affection and prefers to be by himself rather than socialize with his new family. According to the DSM-5, Trevor probably has:
a. oppositional defiant disorder.
b. reactive attachment disorder.
c. post-traumatic stress disorder.
d. a severe cognitive impairment.