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
[{'content': 'Acute infection of hepatitis B virus is diagnosed by: \nSelect and explain. \nA. IgM antibody of Hbs Ag, B. IgM antibody of Hbc Ag, C. IgG antibody of Hbs Ag, D. IgG antibody of Hbc Ag', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' IgM antibody of HBcAg (Ref. November 2001, Micro, Harrison 17/e p 1943-44,1933-34 & 16/e, p 1823-24).", 'role': 'assistant'}]