According to the discussion of spatial visualization, a meta-analysis of the research reported an effect size of 0.19, favoring males. From this information, you can conclude that

a. the average male performed 19% better than the average female.
b. the gender difference is probably due to biological explanations.
c. the gender difference is large enough to explain why more men than women select professions in engineering.
d. the gender difference is small on spatial visualization tasks.

D