What Was the Most Controversial Finding from the Bell Curve

What was the most controversial finding from The Bell Curve by Richard Herrnstein and Charles Murray that sociologists have debunked?

A) Men are innately smarter than women.
B) There are innate intelligence differences by race.
C) Those from elite social groups are innately smarter than those from lower classes.
D) Some individuals are incapable of learning at a college level.