The correct answer is C. Pot A received more sunlight than pot B.
Step-by-step explanation
According to the situation described in the question, the only difference between pot A and pot B is exposure to the sun, since plant A that was located next to the window received more sun than plant B that was enclosed in a closet. It is necessary to remember that plants need sunlight to perform photosynthesis, a process by which they create their food and produce oxygen. According to the above, the reason why the plant of pot A showed better characteristics than pot B, was its exposure to the sun. So, the correct answer is C. Pot A received more sunlight than pot B.