​What Is the Most Common Reason That Vitamin B₁₂ Deficiency,or

​What is the most common reason that vitamin B₁₂ deficiency,or at least compromised B₁₂ status,occurs in older adults?

A) ​Diets are frequently low in vitamin B₁₂,since oral problems and financial difficulties limit meat intake and meats are the best dietary sources of B₁₂.
B) ​Pernicious anemia is common in the elderly.
C) Their diets provide primarily synthetic forms of vitamin B₁₂,which are less absorbable than the protein-bound form found naturally in foods.
D) ​The elderly have a higher incidence of bacterial overgrowth,which decreases secretion of hydrochloric acid.
E) ​B₁₂ supplements are expensive and many older adults cannot afford them.