Red bone marrow is the site of hematopoiesis and produces blood cells.

• A. Yellow bone marrow
• B. Red bone marrow
• C. Compact bone
• D. Cartilage

Answer: (B)

Hematopoiesis happens in red bone marrow because this tissue houses hematopoietic stem cells that differentiate into all blood cell types—erythrocytes, leukocytes, and platelets. In adults, red marrow is found mainly in the axial skeleton and the ends of long bones, where it actively produces blood cells. Yellow marrow, in contrast, is fatty and generally inactive for blood formation. Compact bone is the dense outer layer that gives structure and strength but does not produce blood cells. Cartilage is a separate connective tissue that provides cushioning and support and is not a site of blood cell production.