In the Movie as Good as It Gets, Actor Jack

In the movie As Good As It Gets, actor Jack Nicholson plays Melvin Udall, a gifted writer who always eats in the same restaurant, brings his own plastic utensils, and engages in strict patterns of behavior, such as repetitive hand washing or walking carefully on the sidewalk to avoid stepping on a crack. Failure to follow these ritual behaviors results in extreme anxiety and distress. The character Nicholson was portraying would probably be diagnosed with:

A) dissociative identity disorder.
B) Tourette's disorder.
C) borderline personality disorder.
D) obsessive-compulsive disorder.