B lymphocytes primarily develop in which part of the body?

B lymphocytes, also known as B cells, primarily develop in the bone marrow. The bone marrow is responsible for producing all types of blood cells, including red blood cells, white blood cells, and platelets, as well as the maturation of B lymphocytes. During their development in the bone marrow, B cells undergo a process called somatic recombination which allows them to generate a diverse array of antibodies capable of recognizing numerous pathogens.

Once they have matured, B cells do migrate to other parts of the body, including the spleen and lymphatic tissues, to fulfill their immune functions, such as producing antibodies and responding to antigens. However, it is in the bone marrow where their initial development and maturation take place, making it the correct answer for this question.