The correct option is
A Both assertion and reason are correct and the reason correctly explains the assertion statement
Lymphoid organs are composed of lymphoid tissue, and are the sites of either lymphocyte production and maturation (Primary lymphoid organs such as bone marrow and thymus) or of lymphocyte activation (secondary lymphoid organs).
Lymphocytes are the white blood cells which have a non-granular cytoplasm and can provide immunity against specific foreign substances like pathogens.
Peyer's patches are organized lymphoid tissues, found in the lowest portion of the human small intestine, mainly in the ileum. They are an important part of the mucosa-associated lymphoid tissue (MALT) of the gastrointestinal tract, also known as the gut associated lymphoid tissue or GALT. These lymphoid tissues are rich in the presence of lymphocytes which have migrated there after their maturation in thymus (T-lymphocytes) or bone marrow (B-lymphocytes).
The M cells or microfold cells are specialized epithelial cells in the Peyer’s patches. M cells trap antigens entering the intestinal mucosa and allow the lymphocytes to bind to specific antigens via their surface receptors. This sensitises the lymphocytes to specific antigens and they start proliferating, i.e., dividing and differentiating into different cell types that can launch the necessary immunogenic response to destroy the antigen.
Interaction with the antigen causes the B-lymphocytes to divide and differentiate into plasma cells which produce the antibodies that are specific to particular antigens. Antibodies then bind to antigens and eliminate them. When T-lymphocytes interact with antigens in the secondary lymphoid organs, they divide and differentiate to form different types of T cells (effector cells and memory cells) that have specific functions to provide immunity to the body.
Thus, both assertion and reason are correct and the reason correctly explains the assertion statement.