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 diagnosis of pancreatic cancer (head) is by: \nSelect and explain. \nA. Ultrasound, B. ERCP, C. CT scan, D. Angiography', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. CT scan', 'role': 'assistant'}]