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
Following  cells  are  responsible  for acid secretion in kidney: 
Select and explain. 
A. I cells, B. P cells, C. Mesangial cell, D. Pericytes
A: I cells
Answer: A: I cells 
Explanation: Two types of cells in CD & DCT:
P (Principal) cell is responsible for:

Na+ reabsorption
K+ secretion
H2O Absorption

I (Intercalated) cell: two types

Alpha: acid secretion
Beta: HCO-2 secretion