Strict Vegetarians Are at Risk of Developing a Vitamin B₁₂

Strict vegetarians are at risk of developing a vitamin B₁₂ deficiency because ____.

A) specific foods in their diet inhibit the absorption of vitamin B₁₂
B) their diet causes increased excretion of the vitamin
C) only animal foods contain sufficient amounts of the vitamin
D) their diet increases the rate of use of the vitamin by their bodies
E) vitamin B₁₂ is unavailable in fortified foods