To predict is the likely purpose of which of these presentations? a)the life and times of frederick douglassb)the ways that regular exercise can improve your healthc)the most popular careers in the year 2015d)the reasons for voting against the new tax increase

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.

An adverb clause is the answer?

Are you asking for a opinion ? if so i believe that a speaker should be genuine and honest about what they're saying and should be factual