What Is the Function of the Osmotic Gradient Found in the Kidney

What is the function of the osmotic gradient found in the kidney?

A) to allow electrolytes to move from low to high concentrations in the absence of ATP
B) to permit the precise control of the retention of water and electrolytes
C) to allow the loop of Henle to deliver water to the renal vein
D) to control the filtration of large cells at the glomerulus
E) to permit the excretion of damaged red blood cells