Answer: a) CD4+ T cells and CD8+ T cells
Explanation: Memory T cells are a type of immune cells that contain information regarding the previous infections so, they quickly respond and they fight against to the previous pathogen. Memory T cells include these both subtypes, allowing the immune system to remember and affectively respond to previously encountered antigens.
* CD4+ T cells ==> These are also called as Helper T cells. These cells are helping to other immune cells by releasing cytokines that enhance the immune response. They play vital role in orchestrating the immune response, including helping B cells to produce antibodies and activating other T cells.
* CD8+ Cells ==> These are also called as Cytoxic T cells. These cells directly attacks on cancerous cells. These cells plays vital role for controlling viral infections and targeting cells that have been infected by pathogens.