Suppose that someone says, "A meta-analysis was conducted on gender differences in adolescents' attitudes toward education." From that description, you may infer that the researchers:

a.

asked a large number of experts to provide opinions on the topic.

b.

counted the number of studies that showed more positive attitudes for females, more positive attitudes for males, or no gender differences.

c.

tried to see whether attitudes toward education were correlated with the number of years of education the adolescents had achieved.

d.

statistically combined the results from a large number of previous studies on the topic.