Remark
This is one of those questions that is very hard to pick an answer for. The problem is that all are applicable.
I suppose that the answer you are expected to give is D. D suggests that you need to modest about what you have done to have enough background to deliver the speech in the first place. However it would be a good idea to give some indication of what research has been done, what the stats are on the research, and how many articles these stats represent.
You are very concerned about what the audience knows. You don't want to fill blackboards and blackboards to people who are a casual audience who just want to know how the general what the findings are of those who study climate change as a full time occupation.
You are also very concerned about the best ideas you have about climate change. You don't want to report rumors or hearsay. You want to give a serious representation to a very serious study.
The certainly want to address the concerns of the audience if you know they have any.
