Assertion $A$: Vaccination protects an individual against infection by specific pathogens.
Reason $R$: $B$ and $T$ memory cells produce antibodies in large quantities to neutralize the pathogen attack.
Which option is correct for Assertion $A$ and Reason $R$?

• A
  $A$ and $R$ are both true and $R$ is the correct explanation of $A$.
• B
  $A$ and $R$ are both true but $R$ is not the correct explanation of $A$.
• C
  $A$ is true and $R$ is false.
• D
  $A$ is false and $R$ is true.