Why Are Researchers Less Convinced That Gender-Related Differences in Cognition

Why are researchers less convinced that gender-related differences in cognition and behavior have a physiological basis?

A) These differences have increased over time,due to changes in gender roles.
B) Murder rates are the same in different countries,showing that males are generally more aggressive than females.
C) Males and females no longer differ much in mathematical abilities,although boys are still overrepresented at the lower and higher extremes.
D) All of the above