This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Reason for hyperosmolarity is 
Select and explain. 
A. Increased glomerular capillary pressure, B. Decreased absorbtion of Na+ in PCT, C. Increased activity of Na+ K+ 2cl- ATPase in loop, D. Decreased activity of Na+ K+ ATPase in loop
C: Increased activity of Na+ K+ 2cl- ATPase in loop
Answer: C: Increased activity of Na+ K+ 2cl- ATPase in loop 
Explanation: Hyperosmolarity in the interstitium of kidney is due to activity of na+k+2cl- pump at the ascending limb of loop of henle Ref:Guyton and Hall textbook of medical physiology 12th edition,page:480,481,482