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
[{'content': 'For pulmonary maturation, Which is required during gestation? \nSelect and explain. \nA. Cortisol, B. Surfactant, C. Amniotic fluid, D. Acetylcholine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]