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: Surgery
[{'content': "A pregnant women presents for prenatal care. Her past medical history is significant for a severe illness 3 years ago characterized by fatigue, nausea, anorexia, vomiting, jaundice, joint pains, and generalized skin lesions that slowly disappeareD. She has felt well recently. Which lab test should be ordered to investigate the patient's past illness? \nSelect and explain. \nA. Hepatitis B surface antigen (HBsAg), B. IgG cytomegalovirus (CMV) antibody levels, C. IgM antibody to HBsAg, D. IgM antibody to hepatitis B core antigen", 'role': 'user'}, {'content': 'Answer: A \nExplanation: The woman had acute hepatitis in the past. To determine whether it is resolved or persisted, one should test for HbsAg. Definition of chronic hepatitis is presence of HBsAg for >6months.', 'role': 'assistant'}]