I believe the best answer for this question is B, "the ways that regular exercise can improve your health." This is a prediction because they may not definitively improve your health, but they most likely will. The first answer, the life of Frederick Douglas, is simply biographical information and predicts nothing. The third answer, the most popular careers of 2015, do not predict because 2015 is in the past; it is simply reporting known information. The last answer is based on personal argument, not prediction, leaving you with only one answer. I hope this helps.
