An 8-year-old boy's parents bring him to therapy because of behavioral changes over the past 2 months. He has been very worried about his parents' well-being and becomes very distressed when he leaves home or anticipates leaving them. He has also been refusing to go to school on a consistent basis, stating that he feels sick, but shows no sign of illness. Most recently, he is insisting on sleeping with his parents. These symptoms support a provisional diagnosis of:

a) Reactive Attachment Disorder
b) Adjustment Disorder with mixed disturbance of emotions and conduct
c) Separation Anxiety Disorder
d) Oppositional Defiant Disorder