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': 'Commonest site of feilization is : \nSelect and explain. \nA. lsthmic, B. Ampulla, C. lnfundibulum, D. lnterstitial', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ampulla', 'role': 'assistant'}]