question: Q:A 2-month-old boy is brought to the pediatrician for a routine check-up. His mother says he is feeding well and has no concerns. He is at the 85th percentile for height and 82nd percentile for weight. Immunizations are up-to-date. Results of serum hepatitis B surface IgG antibody testing are positive. Which of the following best explains this patient's hepatitis B virus status?? 
  {'A': 'Window period', 'B': 'Chronic infection', 'C': 'Spontaneous recovery', 'D': 'Vaccination reaction', 'E': 'Passive immunity'},