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
What can be the non-respiratory functions of lungs: 
Select and explain. 
A. Sodium balance., B. Fibrinolytic function., C. Secretion of heparin., D. All of the above.
D: All of the above.
Answer: D: All of the above. 
Explanation: NON respiratory function of lung: 

ACE synthesized by lung – Na balance. 
Fibrinolytic function – Pulmonary Endothelium is rich in PLASMIN activator. 
Heparin – Lung is rich in mast cells which secrete heparin. 
SURFACTANT – Synthesized by type 2 alveolar epithelial cells.