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. Which of the following best describes the purpose of this experiment?
To determine the effect of enclosed spaces on plant growth
To determine the effect of air conditioning on plant growth
To determine the effect of lack of water on plant growth
To determine the effect of sunlight on plant growth