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: Dental
[{'content': 'For the cold testing maximum time of application of cold is: \nSelect and explain. \nA. 5sec, B. 10sec, C. 15sec, D. 20sec', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]