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 pregnacny, characteristic finding in USG is: \nSelect and explain. \nA. Absence of gestational sac in uterus, B. Complex adenexal mass, C. Resistance in coloured Doppler, D. Free fluid in peritoneal cavity', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Absence of gestational sac in uterus Best method of diagnosing unruptured ectopic pregnancy is combination of transvaginal sonography & quantitative B-HCG valuesQ.', 'role': 'assistant'}]