James took two pea plants, placing one in a dark closet and the other on a sunny window sill. Both are located in air conditioned rooms. He then measured the growth of the pea plants after a week. In this experiment sunlight is a(n) ____.
C. Dependent variable without the sunlight he could not preform his experiment because if he where to put both in the sunlight the sunlight would then become control but it could never become independent