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, the dark closet is a(n)

independent variable

Explanation:

Independent variable is controlled by the experimenter; however, the dependent variable depends on the independent variable. Here the dark closet is the independent variable and the growth of the plant is the dependent variable. A dependent variable is measured by the experimenter. An independent variable does not get affected by the experiment.

it's filtration, but this is an assumption so my apologies if i got this