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': 'Tumour marker of endodermal sinus tumour of ovary : \nSelect and explain. \nA. a feto proteins, B. CA 125, C. HCG, D. CEA', 'role': 'user'}, {'content': 'Answer: A \nExplanation: a feto proteins', 'role': 'assistant'}]