The important part for answering this question is: The main syndrome of vitamin B deficiency is pernicious anemia.
This justifies what answer for what question? Q & A: 
Passage: The main syndrome of vitamin B deficiency is pernicious anemia. It is characterized by a triad of symptoms:

Question: Based on this passage, a severe vitamin b12 deficiency results in what form of anemia?
pernicious anemia