Final answer:
Activated B-lymphocytes that do not become plasma cells become C. memory B-lymphocytes.
Step-by-step explanation:
Memory B-lymphocytes are a type of white blood cell that are part of the immune system. They are a subpopulation of B cells that are responsible for retaining a 'memory' of a specific pathogen after an infection is over. This memory allows them to mount a stronger and faster immune response upon subsequent exposures to the same pathogen.
Memory B cells retain the information about a particular pathogen, allowing for a stronger immune response in subsequent exposures to the same pathogen. They do not produce antibodies like plasma cells, but instead contribute to long-term immunity.
For example, when someone receives a vaccine, memory B-lymphocytes are activated and produce antibodies against the weakened or inactive pathogen in the vaccine. If the person is later exposed to the actual pathogen, the memory B cells recognize it and rapidly produce specific antibodies to eliminate the threat, providing lasting immunity. Therefore the correct answer is C. memory B-lymphocytes.