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
The trivalent influenza vaccine contains all of the following strains except: 
Select and explain. 
A. H IN I, B. H3N2, C. H2N 1, D. Influenza B
C: H2N 1
Answer: C: H2N 1 
Explanation: Ans: C. H2N 1Each seasonal influenza vaccine contains antigens representing three (trivalent vaccine) or four (quadrivalent vaccine) influenza virus strains: one influenza type A subtype H1 N1 virus strain, one influenza type A subtype H3N2 virus strain, and either one or two influenza type B virus strains.