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: Medicine
Acute infection of hepatitis B virus is diagnosed by: 
Select and explain. 
A. IgM antibody of Hbs Ag, B. IgM antibody of Hbc Ag, C. IgG antibody of Hbs Ag, D. IgG antibody of Hbc Ag
B: IgM antibody of Hbc Ag
Answer: B: IgM antibody of Hbc Ag 
Explanation: Ans. is 'b' IgM antibody of HBcAg (Ref. November 2001, Micro, Harrison 17/e p 1943-44,1933-34 & 16/e, p 1823-24).