Acquired immunity mediated by which of the following?

Correct option is B. Antibody formation by B-lymphocytes
Immunology is the study of the immune system and its functions. The immune system can function in either specific, adaptive ways or in innate or non-specific ways. The adaptive immune system involves complex antigen-specific immune responses which are specialized and exclusive to certain invaders like bacteria, viruses, and other pathogens. Adaptive immunity is remembered, meaning responses against a re-visiting antigen are increasingly speedy and effective with each future attack. During an initial acquired immunity response, antigens are presented to lymphoid organs (lymph nodes, spleen, tonsils, bone marrow, thymus, etc) so that B-lymphocytes (B cells) and T-lymphocytes (T cells) can be differentiated into effector cells and reproduced. B cells are produced in the bone marrow and are an essential component of the adaptive immune system. A differentiated B cells can also be called a memory B cell and is specific for a certain virus, bacteria, or other pathogen antigen. These memory B cells "remember" the antigen and thus can produce antibodies faster for future invasions.So, the correct answer is "B".