Which of the Following Effects Has NOT Been Demonstrated by Psychologists

Which of the following effects has NOT been demonstrated by psychologists?

A) People undergoing hypnosis can lower their perception of pain.
B) People who comply with a small request are much more likely to later comply with a large request.
C) One portion of the hypothalamus, important for sexual motivation, is more similar in some homosexual men to heterosexual women than it is to that of heterosexual men.
D) Subliminal messages, such as backward speech in music recordings, can strongly influence people's behavior.