Answer:
Option-A
Step-by-step explanation:
Immunity is the natural ability of an organism to protect itself from the pathogen which involves very complex pathways.
The immune response is produced when the pathogen interacts with the organism and the organism in response to activates pathways to eliminate the pathogen.
In the given question, when the person is affected by the same type of pathogen twice, then the second time the memory cells protect the person.
The memory B cells are the cells that are produced by the B lymphocytes during the first-time interaction of the pathogen with the organism. When the second time the person is affected this memory cell gets activated and produces a fast response.
Thus, Option-A is correct.