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
What is true about acute rheumatic fever? 
Select and explain. 
A. Mitral valve is invariably associated, B. Earliest symptom is migratory arthritis, C. Sydenham's chorea is always present., D. It follows streptococcal skin infection
B: Earliest symptom is migratory arthritis
Answer: B: Earliest symptom is migratory arthritis 
Explanation: None