What Is Meant by the "Iron Rule" in Feminist Theory

What is meant by the "iron rule" in feminist theory?

A) Men always have and always will try to dominate women.
B) Women must stand up for and advocate for their rights.
C) Men who conduct research are usually insensitive to women's issues.
D) For psychological and cognitive variables studied, the average difference within each sex is always greater than the average difference between the sexes.
E) Women must learn to rule the household with an iron fist for feminism to prosper.