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: Pathology
[{'content': 'After how many days of radiotherapy, mucositis appear: \nSelect and explain. \nA. 7 days., B. 10 days., C. 14 days., D. 30 days.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: After 12-17 days of radiotherapy, mucositis appears.', 'role': 'assistant'}]