Correct answer: D). The body produces antibodies when it is exposed to the weakened or dead form of a pathogen.
The vaccine consists of a weakened or dead pathogen, in response to that body produces antibodies after the administration of the first dose of vaccine. So, if the same body is exposed to that pathogen in the future the body will memorize it, and attack the pathogen more powerfully because it has already prepared an antibody against that pathogen in order to kill that foreign antigen.
Hence, the correct answer would be option D.