Answer: Bone marrow
Step-by-step explanation:
The facts from your question about the function of erythrocytes, thrombocytes, and leukocytes are true.
Bone marrow is considering spongy tissue that is found in our bones and bone marrow contains stem cells which are important for red blood cells, white blood cells, and platelets.
The stem cells can develop into those three and in that way, the whole body system is connected.