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: Radiology
[{'content': 'Ectopic pregnancy, characteristic finding in USG is - \nSelect and explain. \nA. Absence of gestational sac in uterus, B. Complex adnexal mass, C. Resistance in colored Doppler, D. Free fluid in peritoneal cavity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: "The Presence of a non - ovarian complex adnexal mass is the most sensitive and specific USG finding for ectopic\xa0pregnancy".\n—USG in radiology\n"The presence of a fetal heart beat outside the uterine cavity is pathognomonic for an ectopic pregnancy".\n—USG in radiology', 'role': 'assistant'}]