Correct Option: D

Vitamin B₁₂ is a “generic descriptor for compounds exhibiting the biologic activity of cyanocobalamin; the antianemia factor of liver extract that contains cobalt, a cyano group, and corrin in a cobamide structure. Vitamin B₁₂ is vital for the formation of red blood cells, as well as for the proper functioning and health of nerve tissue. If left untreated, vitamin B₁₂ deficiency, also known as B₁₂ deficiency, can lead to anemia, as well as nerve and brain damage, which may eventually become irreversible.