This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Physiology
[{'content': 'Surfactant is: \nSelect and explain. \nA. Protein, B. Glycoprotein, C. Sphingolipid, D. Alpha palmitoyl lecithin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D', 'role': 'assistant'}]