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: Medicine
True statement about Rheumatic fever in childrena) Polyarthritisb) Caused by α hemolytic streptococcic) Most common valve involvement is Mitrald) Erythema marginatum is common in face 
Select and explain. 
A. bc, B. cd, C. ac, D. ab
C: ac
Answer: C: ac 
Explanation: None