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: Microbiology
[{'content': "Causative agent of acute rheumatic fever: \nSelect and explain. \nA. Group `A' b-hemolytic streptococcus, B. Group -B b-hemolytic streptococcus, C. Group -C b-hemolytic streptococcus, D. Group -D b-hemolytic streptococcus", 'role': 'user'}, {'content': "Answer: A \nExplanation: Group `A' b-hemolytic streptococcus", 'role': 'assistant'}]