Elena Changes Her Attitude About Nuclear Weapons After Giving a Speech

Elena changes her attitude about nuclear weapons after giving a speech supporting their development to a group of classmates.Brett gives the same speech,but to an empty classroom,and does not change his attitude.Which of the following theories does the difference between Elena and Brett support?

A) self-esteem theory
B) impression-management theory
C) self-perception theory
D) self-affirmation theory