Answer:
The correct answer would be the third option.
Vaccination refers to the administration of weekend or attenuated microorganism or antigen in the body. It helps in developing adaptive immunity in the body.
Thus, vaccine neither wears out with time nor body eliminates the vaccine.
However, the flu virus changes every year due to the short life cycle. Consequently, the memory B cells cannot recognize changed virus due to which the body loses its immunity against the virus.
This is why doctors recommend that people should get flu shot each new flu season.