I believe that the answer is D. The general purpose of the speech is that you provide an argument for a topic with your support and provide counters to the counter arguments for the topic itself. Your main purpose should be to prove the audience believe that you are correct in what you are explaining and talking about.
Answer is this
D-the author is speculating but not proving concrete evidence
This seems like it belongs more in the catagory of history but if the author is Thomas Jefferson, or any president from Jefferson until the Civil War than they are most likely for it