This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'The following is a marker of acute hepatitis B infection: \nSelect and explain. \nA. DNA polymerase, B. Hepatitis core antigen, C. Anti HBs, D. IgG to core antigen', 'role': 'user'}, {'content': 'Answer: A \nExplanation: HBV-DNA can be measured by PCR in the blood. Viral loads are usually in excess of 105 copies/mL in the presence of active viral replication, as indicated by the presence of e antigen. In contrast, in individuals with low viral replication, who are HBsAg- and anti-HBe-positive, viral loads are less than 105 copies/mL.\nReference: : Davidson P R I N C I P L E S\xa0 \xa0and Practice O F M E D I C I N E 23rd edition page no\xa0 875', 'role': 'assistant'}]