What Is the Primary Reason for the Difference in Strength

What is the primary reason for the difference in strength between males and females?

A) Females have increased testosterone levels, which decreases their ability to develop muscle bulk.
B) Females have smaller muscle fibers than males do.
C) Females are incapable of building significant muscular strength.
D) Females have a higher percentage of body fat, which decreases the strength/body weight ratio.