Which organ system is responsible for producing white blood cells in humans?

• A. Digestive system
• B. Nervous system
• C. Immune system
• D. Endocrine system

Answer: (C)

White blood cells are the body's defense cells that fight infections. They’re produced in bone marrow and then circulate as part of the immune response. Among the options, the immune system is the one closely tied to these cells: it uses and coordinates white blood cells to recognize and attack pathogens. The other systems have different primary roles—digestion, signaling, or hormone control—and do not govern the production or primary function of white blood cells.