This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excretory System (Kidney, Bladder) Acid-Base Balance, Subject name: Physiology
A major fraction of filtered potassium is absorbed in: 
Select and explain. 
A. Collecting duct, B. Distal convoluted tubule, C. Proximal convoluted tubule, D. Thick ascending limb of loop of Henle
C: Proximal convoluted tubule
Answer: C: Proximal convoluted tubule 
Explanation: Potassium is filtered at the glomerulus, reabsorbed & secreted by tubules, and is excreted in urine. Of the total K+ ingested in the diet, 90-95% is excreted. PCT :reabsorbs about 67% of the filtered K+ under most conditions; 20% of the filtered K+ is reabsorbed by the LOH. The two most impoant physiologic regulators of K+ secretion Plasma Aldosterone. Other factors include a Flow rate of the tubular fluid, acid-base balance, glucocoicoids.