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
Marker for acute viral hepatitis caused by HBV: 
Select and explain. 
A. IgM anti-HBc Ag, B. IgG anti-HBc Ag, C. IgM anti-HBs Ag, D. IgG anti-HBs Ag
A: IgM anti-HBc Ag
Answer: A: IgM anti-HBc Ag 
Explanation: Ans. a. IgM anti-HBcAg