What Finally Motivated the American Psychiatric Association to Remove Homosexuality

What finally motivated the American Psychiatric Association to remove homosexuality as a diagnosis from the Diagnostic and Statistical Manual of Mental Disorders (DSM) ?

A) Protests at the APA convention in 1970.
B) Research results which proved that homosexuality is not a mental disorder.
C) The compelling testimony of members of the LGBTQ community.
D) The APA definition of a mental disorder which says that symptoms must cause significant distress or be associated with significant impairment.