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: Gynaecology & Obstetrics
[{'content': 'All are fetal membranes EXCEPT : \nSelect and explain. \nA. Chorion, B. Amnion, C. Decidua capsularis, D. Yolk sac', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Yolk sac', 'role': 'assistant'}]