This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Tubal Pregnancy, Subject name: Gynaecology & Obstetrics
[{'content': 'A young female with 2 month amenorrhea presents with sudden abdominal pain with adnexal mass, urine pregnancy test is positive. Most likely diagnosis: \nSelect and explain. \nA. Ovarian tumor, B. Ectopic pregnancy, C. Pelvic tumor, D. Ovarian cyst', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. b. Ectopic pregnancy (Ref: William's Obstetrics 22/e p253, 265)", 'role': 'assistant'}]