The answer is A: an interview with a sports reporter for a major magazine who specializes in youth sports.
An unbiased source is one that could provide an argument based on expertise, experience, and solid research, taking into consideration a matter of argumentation in all of its nuances, and not just a one-sided view. A sports reporter gathers all this attributes and is a credible source since, being part of the media, he or she is expected to comply with the norms and guidelines of reporting and research, which are: objectivity, soundness of arguments, responsibility, accuracy, and the possibility of corroborating his or her arguments by means of others´ founded arguments.