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: Social & Preventive Medicine
[{'content': 'All the following are true regarding Type A influenza virus, EXCEPT: \nSelect and explain. \nA. There are only 14 subtypes of haemagglutinin, B. There are only 9 subtypes of neuraminidase antigen, C. Humans are generally infected by virus of subtype H1, H2 or H3 and N1 or N2., D. It shows both antigenic shift and drift', 'role': 'user'}, {'content': 'Answer: A \nExplanation: There are 16 subtypes of hemagglutinins. Rest of the statements given are true. Antigenic changes occurs only to a lesser degree in group B influenza virus. Influenza C virus appears to be antigenically stable. Note: Almost all of the pandemic which has ever occurred is due to Type A influenza virus. Ref: Park, Edition 21, Page - 143,144', 'role': 'assistant'}]