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: Medicine
Which of the following aquaporin water channels is located on apical membrane of principal cells of the collecting duct 
Select and explain. 
A. Aquaporin 1, B. Aquaporin 2, C. Aquaporin 3, D. Aquaporin 4
B: Aquaporin 2
Answer: B: Aquaporin 2 
Explanation: Aquaporin 2 (AQP 2) water channels are located on the apical membrane.