Which rigid organ contains marrow and creates red blood cells?

• A. Bones
• B. Skin
• C. Pancreas
• D. Brain

Answer: (A)

The key idea here is where red blood cells come from. Red blood cells are produced through hematopoiesis inside the bone marrow, which sits inside rigid bones. So bones are the organ that contains marrow and creates red blood cells.

The other organs don’t contain marrow or generate blood cells: skin isn’t involved in blood formation, the pancreas handles digestion and blood sugar, and the brain controls the nervous system.