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
Non-respiratory function of lungs ? 
Select and explain. 
A. Anion balance, B. Sodium balance, C. Potassium balance, D. Calcium balance
B: Sodium balance
Answer: B: Sodium balance 
Explanation: Ans. is 'b' i.e., Sodium balance(Ref: Lecture notes on human physiology 4th/e p. 400]One of the most impoant metabolic (non-respiratory) function of lungs:As a pa of renin-angiotensin-aldosterone system, lungs indirectly regulate sodium and water balance (and BP).However, lungs also directly affect Na+ balance is epithelial Na+ channels (E NaCs).