Final answer:
Calcium (D) is not necessary for erythropoiesis. Folic acid, vitamin B12, and copper are essential nutrients for red blood cell production.
Step-by-step explanation:
Of the given options, Calcium (D) is not necessary for erythropoiesis. Erythropoiesis is the process of red blood cell production. The nutrients necessary for erythropoiesis include folic acid, vitamin B12, and copper. Folic acid and vitamin B12 are important for DNA synthesis, while copper is necessary for the production of hemoglobin. Calcium, on the other hand, is not directly involved in erythropoiesis.