This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Epidemiologic study of Hepatitis B is by - 
Select and explain. 
A. Hbe Ag, B. HBc Ag, C. HBs Ag is used, D. Anti HBc
D: Anti HBc
Answer: D: Anti HBc 
Explanation: Anti HBc appears in serum a week or two after the appearance of HBs Ag. It is earliest antibody marker seem in blood.&remainlifelongg,it is an indicator of prior infection with HBV REF:MICROBIOLOGY ANANTHA NARAYANAN NINTH EDITION PAGE546