This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hepatitis, Subject name: Medicine
[{'content': 'Antigen which does not appear in blood in hepatitis B: \nSelect and explain. \nA. HbcAg, B. HbeAg, C. HbsAg, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Because HBcAg is intracellular and, when in the serum, sequestered within an HBsAg coat, naked core paicles do not circulate in serum and, therefore, HBcAg is not detectable routinely in the serum of patients with HBV infection. By contrast, anti-HBc is readily demonstrable in serum, beginning within the first 1-2 weeks after the appearance of HBsAg and preceding detectable levels of anti-HBs by weeks to months.', 'role': 'assistant'}]