A student wants to determine the effect of soil type on plant growth. He set up 3 pots as shown below. How could this experiment be improved?
A - There is nothing wrong with this experiment.
B - The three pots should have different amounts of water
C - All three pots should have the same kind of seed, the same amount of light, and the same amount of water.
D - All three pots should have the same kind of soil.