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': 'Best for unruptured ectopic pregnancy is: \nSelect and explain. \nA. Per abdominal US, B. HCG, C. Trans vaginal US, D. Amniocentesis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Tranvaginal US', 'role': 'assistant'}]