What is the primary function of white blood cells?

The primary function of white blood cells is to fight infections. White blood cells, or leukocytes, are a crucial part of the immune system, which protects the body against both infectious disease and foreign invaders. They identify and eliminate pathogens such as bacteria, viruses, and other microorganisms. There are different types of white blood cells, including neutrophils, lymphocytes, and monocytes, each playing unique roles in immune response, such as attacking and destroying pathogens or coordinating the immune response.

The other options relate to different biological functions: the transport of oxygen is primarily conducted by red blood cells; blood clotting is facilitated by platelets and specific proteins in plasma; and the regulation of body temperature involves various systems such as the hypothalamus, skin, and blood vessels, rather than the action of white blood cells. Thus, C is the most accurate representation of what white blood cells do.