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
What are the major functions of "I" cells? 
Select and explain. 
A. Reabsorb potassium ion., B. Secrete potassium ion., C. Excrete potassium ion., D. All of the above
A: Reabsorb potassium ion.
Answer: A: Reabsorb potassium ion. 
Explanation: Reabsorb potassium ion.REABSORPTION IN LATE DISTAL TUBULE:Functionally similar to coical collecting tubule.Facultative type:Reabsorption of solutes/water depends on water/electrolyte balance.Hence, "Facultative type" of absorption.Cells involved in reabsopion:Principal (P) cells.Intercalated (I) cells.FUNCTIONS OF 'I' CELLS:Reabsorb potassium ion.Secrete hydrogen ions into tubular lumen.