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': 'Large painful ulcers seen in which grade of mucositis: \nSelect and explain. \nA. Grade 1., B. Grade 2., C. Grade 3., D. Grade 4.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 4 grades\n\nGrade 1: \xa0whitish area Asymptomatic\nGrade 2: \xa0ulcers(Small)\nGrade 3: \xa0large (painful)\nGrade 4: entire oral mucosa.', 'role': 'assistant'}]