Answer:
Option (d).
Explanation:
Immunity may be defined as the ability of individual to fight against the pathogens. The main cells that are involved in the immunity are B cells and T cells.
B cells produce two types of cells - plasma cells and memory cells. Plasma cells multiply rapidly whereas memory cells will create the memory of the pathogen and protect the body against the pathogen at second time. Memory cells not the plasma cells on the reexposure of pathogen.
Thus, the correct answer is option (d).