Qualitative predictor variables are entered into a regression model through dummy variables.

Diana is a bright student, but she procrastinates. She puts off writing term papers and gets incomplete grades from her teachers which eventually become F's. Diana's therapist has her write down her thoughts about work, read the thoughts as if someone else had said them, and then write a rational response to each one. The treatment method used to help Diana deal with her problem is:

A) psychodynamic therapy.
B) behavior therapy.
C) cognitive therapy.
D) humanist therapy.