Suppose That I Suspect That the Size of My Pumpkins

Suppose that I suspect that the size of my pumpkins is primarily determined by the amount of sunlight each one receives.How could I use the method of concomitant variations to confirm this?

A) Grow all of my pumpkins in the garage to see whether they end up being smaller.
B) Grow one pumpkin in an exposed area, another in a somewhat shaded area, and another in a very shaded area to see whether their sizes differ.
C) Grow pumpkins from three different seed packets and then measure their sizes.
D) Give some pumpkins more water and some pumpkins less water and then observe their sizes in order to rule out watering as the cause.
E) Shine a flashlight on each pumpkin for one hour each night to see whether or not the pumpkins get bigger.