Answer:
B. To show the reader that you have listened to what others have to say
Step-by-step explanation:
An argumentative essay includes a comprehensive discussion on a subject in question, as well as weighty arguments that can convince the reader of accuracy from the author's point of view. Once the author exposes his point of view it is important that he / she show a counterclaim, because so the author shows that he has evaluated all sides of a subject, heard opinions different from his. This passes credibility and shows that the author has a broad knowledge on the subject.