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
Causative agent of acute rheumatic fever: 
Select and explain. 
A. Group `A' b-hemolytic streptococcus, B. Group -B b-hemolytic streptococcus, C. Group -C b-hemolytic streptococcus, D. Group -D b-hemolytic streptococcus
A: Group `A' b-hemolytic streptococcus
Answer: A: Group `A' b-hemolytic streptococcus 
Explanation: Group `A' b-hemolytic streptococcus