Which of the Following Has Not Been Demonstrated in Research

Which of the following has not been demonstrated in research on role-playing?

A) People show greater attitude change after writing a persuasive speech than after reading one.
B) Self-generated arguments are better remembered than arguments provided by others.
C) Expecting to have to present a persuasive communication to another person increases the impact of the communication.
D) Role-playing effects are stronger among those low in need for cognition than those high in need for cognition.