The correct answer is Bone Marrow. Bone marrow actually exists inside the bones. The bone provides protection for the bone marrow so that it is less likely to be harmed or damaged.
I would say the Bone marrow it's like a thick, spongy kind of jelly inside your bones. it makes all kinds of blood cells: red blood cells that carry oxygen, white blood cells that fight infections, and platelets that help blood clot.
