The Clinic Clients Respond Negatively to the Need for a Yearly

The clinic clients respond negatively to the need for a yearly flu shot. They ask why the medical communities don't just create one shot that will last for several years. Which is the best response from the nurse?

A) Genetic changes in the bacteria that cause the flu require a rotating course of antibiotics
B) Genetic changes make the flu virus resistant to the flu shot from year to year
C) There is more than one strain of the flu virus and you must be protected from all of them
D) The shots last only for 3 to 6 months and must be renewed on a yearly basis