I can't really answer question 3 or 5 due to not seeing the passage or the picture to said passage, but I can answer question 4 for you. I would say the answer to 4 would be a.
I believe the answer is D. investigative
The author's argument would be most effectively strengthened by using reliable sources and precise data. Without any cold hard facts, all of these points that the author has provided may be considered assumptions, so with facts and reliable sources, the information will be much more reliable.
