Ans. is 'c' i.e. IgM anti-HBc You are sure to get questions on serological marker of Hepatitis in every PG exams (particularly AIIMS & AI). This topic has been thoroughly discussed.See Q. No 58 of Nov. 2001.Coming to the question; Hbs Ag is also present in recent hepatitis B infection but it is not a reliable marker because it can also be seen in carriers, whereas IgM anti- HBc is seen only in acute or recent hepatitis and is replaced by IgG anti Hbc in chronic infections.