A new government policy has been developed to avoid many serious cases of influenza. This goal will be accomplished by the annual vaccination of high-risk individuals: everyone 65 and older as well as anyone with a chronic disease that might cause them to experience complications from the influenza virus. Each year' s vaccination will protect only against the strain of the influenza virus deemed most likely to be prevalent that year, so every year it will be necessary for all high-risk individuals to receive a vaccine for a different strain of the virus. Which one of the following is an assumption that would allow the conclusion above to be properly drawn?
A: The number of individuals in the high-risk group for influenza will not significantly change from year to year.
B: The likelihood that a serious influenza epidemic will occur varies from year to year.
C: Each year the strain of influenza virus deemed most likely to be prevalent will be one that had not previously been deemed most likely to be prevalent.
D: No vaccine for the influenza virus protects against more than one strain of that virus.
Choose A, B, C or D as your solution.
C