Which of the Following Involves a Test of K-Independent-Samples

Which of the following involves a test of k-independent-samples?

A) Test of differences in the percent of men and women who are or are not members of Greek organizations on campus
B) Test of the average incomes of subscribers of Southern Living and Better Homes and Gardens
C) Test of whether the mean salary of professors at Metro University is higher than the national average for university professors
D) Test of whether a change occurred in the proneness for heart disease among people who switched to a diet high in fish
E) Test of differences in ad recall among three experimental groups (each of which saw a different advertisement) and a control group