For this problem, the best way out of the presented options would be to B. publish his findings in research journal.
Dr. Peterson has experimented with the medicinal properties of some plants. These results might be useful for other researchers or might even be a breakthrough and that he doesn't know it yet. If he wants to communicate the results to students and researchers, the best method to share his results would be to publish his findings in a research journal. This would not just spread the word to those that he can gather in a get-together, and not just his local folks in his town, but throughout the whole world.