Answer :
Answer: Option A.
nephron loop multiplies the concentration of salts in the interstitial fluid of the kidney medulla.
Explanation:
countercurrent multiplier is a system that utilize energy that create osmotic gradients and enable reabsorption of water thereby increase concentration of urine. The countercurrent multiplier uses electrolyte pumps there by making the nephron loop increase the concentration of salts in the interstitial fluid of the kidney medulla because it allows the nephron to reabsorb alot of water and and increase the concentration of urine for excretion while at the same time using as little energy as possible.