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': 'Occult hepatitis B is: \nSelect and explain. \nA. HBV DNA < 104 copies/ml with HBsAg negative, B. HBV DNA < 104 copies/ml with HBsAg positive, C. HBV DNA < 104 copies/ml with HBeAg negative, D. HBV DNA < 104 copies/ml with HBeAg positive', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Occult hepatitis B is defined by the presence of HBV DNA in serum or liver in the absence of HBsAg. Serum HBV level is usually less than 104 copies/ml. Occult HBV infection has been found in patients with HCC, past HBV infection, or chronic hepatitis C, and individuals without HBV serological markers.', 'role': 'assistant'}]