I think they are good and bad
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.
The surface area of a sphere can be approximated as follows: Surface area = 4πr2; where r is the radius of the sphere; π is a constant that is roughly equal to 3.