Infection with hepatitis D virus (HDV, delta agent) can occur simultaneously with infection with hepatitis B virus (HBV) or in a carrier of hepatitis B virus because HDV is a defective virus that requires HBV for its replicative function. What serologic test can be used to determine whether a patient with HDV is an HBV carrier?

A. HBsAg
B. HBc IgM
C. HBeAg
D. HBs IgM
E. HBs IgG