Which of the Following Best Reflects Psychology's Goal of Description

Which of the following best reflects psychology's goal of description?

A) Researchers have studied how smoking habits develop so that they may develop techniques to prevent teenagers from starting the habit.
B) Researchers have developed a test that shows which individuals are likely to develop Alzheimer's disease.
C) Researchers have examined hundreds of cases of dissociative identity disorder (multiple personality) in order to provide a clear picture of the disorder.
D) Researchers have identified a gene involved in many cases of obesity.