Final answer:
Vitamin B12 is used for the treatment of pernicious anemia option (A).
Step-by-step explanation:
Vitamin B12 is used for the treatment of pernicious anemia option (A). Pernicious anemia is caused by poor absorption of vitamin B12 and is often seen in patients with Crohn's disease, surgical removal of the intestines or stomach, intestinal parasites, and AIDS.
Administering vitamin B12, often in the form of injections, is a common treatment for pernicious anemia. By providing B12 directly, it bypasses the need for absorption through the digestive system, ensuring that the body has an adequate supply of this essential vitamin for the production of red blood cells and the maintenance of neurological function.