Which of the following best describes lymphocytes?

Lymphocytes are a type of white blood cell that play a crucial role in the immune response of the body. They are primarily involved in identifying and attacking pathogens such as bacteria and viruses, thereby fighting infections. Lymphocytes include several subtypes, such as T cells, which can kill infected host cells, and B cells, which can produce antibodies specific to antigens presented by pathogens. This makes option C the most comprehensive choice, as it encapsulates the primary function of lymphocytes in the immune system.

Other options describe different components or types of cells in the body. For instance, red blood cells are responsible for oxygen transport, and cells involved in blood clotting are typically platelets or coagulation factors, not lymphocytes. Antibody-producing cells are specifically B cells, which, while they are a type of lymphocyte, do not represent the broader function of all lymphocytes in fighting infections. Therefore, while option C accurately describes lymphocytes, the other options refer to different cellular roles and functions.