This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pathology
[{'content': 'Valve usually not involved in rheumatic fever \nSelect and explain. \nA. Mitral, B. Aoic, C. Pulmonary, D. Tricuspid', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The mitral valve alone is involved in 70% of cases, with combined mitral and aoic disease in another 25%; the tricuspid valve usually is less frequently (and less severely) involved; and the pulmonic valve almost always escapes injury. (Robbins basic pathology,9th edition,pg no.391)', 'role': 'assistant'}]