15 . ( 3 points ) Which of the following comparisons would use a t - test comparing two independent groups A . Fifteen retirees with diagnosed hypertension are assigned a program of diet , exercise , and meditation . A baseline measurement of blood pressure is taken before the program begins and again after 2 months . Was the program effective in reducing blood pressure of the participants after analyzing the mean blood pressure before the program compared to mean blood pressure after the program ? B . Comparing average GPA of male undergraduate students vs average GPA of female undergraduate students C . Comparing average age of freshman sophomores , juniors , and seniors D . Comapring the average GPA of economics majors , biology majors , and computer science majors