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: Surgery
[{'content': 'Gold standard test in insulinoma - \nSelect and explain. \nA. CT scan, B. Ultrasound, C. MRI, D. Aeriography', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Answer \'b\' i.e. Ultrasound "The most impoant examination is intraoperative ultrasound, which can identify a pancreatic tumor in nearly all cases. It is more sensitive than any preoperative test." - CSDT', 'role': 'assistant'}]