Leads to wrong conclusion. We’re not trying to explain what the attacks result from. We’re trying to prove that they should be avoided. (A) allows us to explain why someone makes a character attack. It doesn’t help us conclude that someone shouldn’t use a character attack.

Lead to wrong conclusion. We’re not trying to prove that people shouldn’t be impressed by character attacks. We’re trying to prove that these attacks shouldn’t be used.

Provides a bridge that gets us from the premises to the conclusion. (C), rephrased, means that if a debating technique does not confront every argument, then it should be avoided. We know from a premise that character attacks “do not confront the opponent’s argument.” So, we know that these attacks don’t confront every argument — there’s at least one argument that’s not confronted by a character attack. (C) allows us to conclude, then, that we should avoid making a character attack.

Leads to wrong conclusion. We’re not trying to prove that character attacks threaten one’s own moral right to enter a debate. We’re trying to prove that the attacks should be avoided.

Leads to wrong conclusion. We’re not trying to prove that questions of character should be raised. We’re trying to prove that character attacks should be avoided.