Visual learners are able to translate an algebraic equation into visual problem, therefore it aligns with their strength of solving problems from a visual point of view as in the case of geometry.

Which of the following, if true, helps to explain why some people who are visual are able to excel in algebra?

(A) Those people can formulate an algebraic problem into something visual.---Correct- Because as geometry deal with figures, which can be visualized. Similarly, when algebraic problems can be visualized those can be solved as well by the people who excel in algebra
(B) Those people have developed an interest and appreciation for non-visual applications.-Irrelevant- Interest and appreciation not discussed in the argument
(C) Those people can solve many geometric problems by different methods and approaches.-Irrelevant- methods and approaches not discussed in the argument
(D) Those people can solve the most difficult geometric problems without much effort.--Irrelevant
(E) Those people have taken many algebra courses before having taken geometry.-Out of scope

Hope this helps

it is A, the main idea of this passage is dealing with visual learner.
"visual learner usually excel in geometry more than in algebra".
and based on that what explain why some visuals can excel in algebra ONLY because they can visualize it.