In 2003, despite the popularity of diets that focused on an

First, the number should jump to X, not jump at X. --> A, D, E are wrong.
Secondly, because "in 2003" indicates past tense, present perfect tense in A, C, is wrong.
Thus, only B remains and is correct.

In 2003, despite the popularity of diets that focused on an increase in the consumption of animal proteins, the number of United States citizens considering themselves "vegan" has jumped by almost 100 percent, at 5 million.


(A) considering themselves "vegan" has jumped by almost 100 percent, at
Wrong.

(B) considering themselves "vegan" jumped by almost 100 percent, to
Correct.

(C) who considered themselves "vegan" has jumped by almost 100 percent, to
Wrong.

(D) who considered themselves "vegan" jumped almost by 100 percent, at
Wrong.

(E) to consider themselves "vegan" jumped almost by 100 percent, at
Wrong.

Hope it helps.