Dr Lewis Has Recruited 100 Subjects to Be in His

Dr. Lewis has recruited 100 subjects to be in his study on personality traits. He knows that many of them differ with respect to education, socioeconomic status and religion. To equally distribute these differences across the four groups he will use in this study, Dr. Lewis should

A) assign subjects to groups using a counterbalancing procedure.
B) randomly assign subjects to the groups.
C) provide operational definitions for education, socioeconomic status, and religion.
D) design the study so the effects of these variables on personality can also be measured.
E) provide a valid operational definition of the dependent variable.