This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Medicine
Marker for active HBV ? 
Select and explain. 
A. HBsAg, B. HBcAg, C. JgM anti HBSAg, D. IgG anti HBSAg
A: HBsAg
Answer: A: HBsAg 
Explanation: <P>Davidson&;s principles and practice of medicine 22nd edition. *HBs Ag is an indicator of active infection and a negative test for HBs Ag makes HBV infection very unlikely.HBcAg is not found in blood but antibody to it appeared in the blood.</p>