I believe the answer is the weight of each tomato.
This is because the weight of each tomato depends on the amount of fertilizer (the independent variable/the thing being changed) added to each plant.
What controls what molecules pass in and out of a cell?
Answer - B. Kidney function is controlled by the blood's composition and hormones.
Reasoning - Well to start off the kidneys (main) purpose function is to clean your blood which is very Important with blood composition. Second It can also and will excrete it through urine which is pretty much what it does. Oh and also a little bit of hormones.