This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Over half of the potassium that appears in the urine of a patient, who has ingested some potassium salts, is derived from 
Select and explain. 
A. Glomerular filtrate, B. Secretion by the distal tubule, C. Reabsorption in the proximal tubule, D. Secretion by the loop of Henle
B: Secretion by the distal tubule
Answer: B: Secretion by the distal tubule 
Explanation: In Normal K+ intake -
-        The proportion of K+ by filtration in urine- 2/3
-        The proportion of K+ by secretion in urine (Distal tubules and collecting duct)- 1/3
In High K+ intake-  
-        The proportion of K+ by filtration in urine- 1/3
-        The proportion of K+ by secretion in urine (Distal tubules and collecting duct)- 2/3