B. Explain in a polite way why your argument uses facts more effectively.
It's important to prove the counterclaim wrong or at least why it isn't as good of an option as your argument. It's also important to do this in a way that is polite. Sometimes an author might write that a person who agrees with the counterclaim is silly or lacking intelligence - this is not polite, nor does this intelligently dispel the counterclaim's ideas.
The other options are simply wrong. If you wanted the readers to ignore the counterclaim, you shouldn't even write it. Option C is wrong because a counterclaim is supposed to counter your claim. If you change your claim, then you need to change the counterclaim. Leaving out the counterclaim is also not an option because if you do not address the counterclaim, then you're not writing an effective argument essay.