d) It makes the argument balanced and can show why the original claim is stronger.
The counterclaim is used to address any big opposing arguments the audience could make against the claim. This allows the speaker to invalidate any counterclaims. By doing this, the original claim is stronger because the opposition is squashed. It also makes the speaker more reliable and the argument more balanced because it shows that the speaker is aware of other opinions and not ignorant to other thoughts and ideas. It makes the speaker's position more valid and seemingly well considered.