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
An important non-respiratory function of lungs is: 
Select and explain. 
A. Anion balance, B. Sodium balance, C. Potassium balance, D. Ca2+ balance
B: Sodium balance
Answer: B: Sodium balance 
Explanation: None