An IV-drug user discovered that a friend with whom he shared needles for injections was diagnosed with viral hepatitis. He had his blood drawn at the local public health clinic and tested for HBV. Which of the following markers is usually the first viral marker detected after infection with HBV?

The markers of HBV infection, in order of appearance, are hepatitis B surface antigen (c), hepatitis e antigen (b), anti-hepatitis B core antigen IgM (e), and anti-hepatitis B e antigen (d), followed by anti-hepatitis B surface antigen IgG if the infection resolves. Hepatitis B core antigen (a) is found only in the nuclei of infected hepatocytes and not free in the bloodstream, although it is present in circulating intact hepatitis B virions (originally called "Dane particles").