GREY!

the virus game was just lsac trying to get us to solve their tech problems

Ad hominem isn't always fallacious reasoning. In cases where the credibility of the author casts doubt on the reliability of their claims, it is perfectly reasonable to point this out.

For example, if claimed that women shouldn't be allowed to use pain killers during childbirth because I think the pain is all in their heads, you might point out that since I'm a single man with no children, no possibility of ever giving birth, and have no expertise in pain, there is certainly doubt to the credibility of this claim.

After all, what the hell do I know about the pains of childbirth?

On the other hand, if you said that my argument is invalid because you don't like the colour of my hair, that would be fallacious reasoning. The colour of my hair has no relevance to my argument (even if my argument is shitty).

From the stimulus:

"Illustrating algebraic concepts graphically would be equally effective pedagogically, even though the deepest mathematical understanding is abstract, not imagistic."

So: images can provide some mathematical understanding, just not the deepest mathematical understanding. Now, when we look at answer choice B:

B) People who are very good at manipulating symbols do not necessarily have any mathematical understanding.

So: This answer contradicts the premise that symbols can provide some mathematical understanding.

Hope that helps.