challenge: According to some psychologists, what may be a contributing factor to the difference in mathematics performance between boys and girls?
  
  A. Differences in the quality of math education received by boys and girls in schools
  B. Variations in the amount of time spent on math homework by boys and girls
  C. Biological differences in brain structure between males and females
  D. Differences in the way parents perceive and encourage mathematical achievement in sons versus daughters
  Answer: 