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 
Select and explain. 
A. Anion balance, B. Sodium balance, C. Potassium balance, D. Calcium balance
B: Sodium balance
Answer: B: Sodium balance 
Explanation: Extracellular ACE on the surface endothelial cells in pulmonary circulation activates Angiotensin I to Angiotensin II.
It also directly affects sodium balance through epithelial sodium channels.