According to the statement, the speaker agrees with the person's point of view, hence Option D is the correct answer because "dispelled" means to make disappear, so it is correct to say that all the doubts(a feeling of uncertainty) of the speaker disappeared after listening.
Option A is incorrect because "confirmed" means to "state the establishment of as a sure thing", so it is incorrect because if the doubts are confirmed, then the speaker cannot agree to his point of view which would contradict his statement.
Option B is incorrect because the statement is being made with respect to arguments and opinions and not the presence of friends.
Option C is incorrect because " the speaker is listening and not talking, hence it is incorrect.