The correct option is D RBCs
Bone marrow is the flexible tissues in the interiors of the bones. Bone marrow can be either red or yellow depending upon the red or hematopoietic or yellow or fatty tissue.
In humans, the red bone marrow forms all the blood cells except for lymphocytes. Also, it contributes to the destruction of RBCs along with liver and spleen,
Yellow marrow serves mainly as a storehouse for fats but may be converted to red marrow under certain conditions (like severe blood loss).
Thus, the correct answer is option (D), 'RBCs'.