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
In  a  normally  functioning  kidney, which part of the tubule has the lowest permeability to water during anti­diuresis? 
Select and explain. 
A. A, B. B, C. C, D. D
C: C
Answer: C: C 
Explanation: The thick ascending limb is relatively impermeable to water even under conditions of maximal antidiuresis.