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': 'The fastest dental film currently available has the speed\nrating of \nSelect and explain. \nA. "D" speed, B. "C" speed, C. "F" speed, D. "E" speed', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]