Thanh Was in a Car Accident a Year Ago in Which

Thanh was in a car accident a year ago in which she suffered some brain damage. Because of the rare nature of her impairment, Dr. Morello kept very detailed notes concerning the treatments administered, the effects of those treatments, and other particular aspects of Thanh's condition. He hopes to publish his findings so that if another psychologist encounters a patient with a condition like Thanh's, that psychologist will have some information to aid him or her in treating that individual. Which research method is Dr. Morello using?

A) Controlled experiment
B) Case study
C) Naturalistic observation
D) Survey