For those interested, here is the official explanation from The Princeton Review:
In the question stem, the phrase can most reasonably be concluded indicates this is an inference question. Do not bother breaking the passage into its conclusion, premise, and assumption for inference questions. Instead, focus on what the passage states directly. The correct answer must be true based on the facts of the passage. The passage presents information about the requirements for understanding political speeches, listing a finely-tuned ear, an understanding of the subtleties of political language, and [familiarity] with controversies...among the electorate when the speaker pays respect to the concerns of his many constituents. Evaluate the answer choices.
Choice A: No. This choice is out of scope. The passage provides no information to judge the speaker's oratorical skills, nor to infer that promises and platitudes are necessary to satisfy constituents.
Choice B: No. This choice is out of scope. This choice is tempting, as the passage begins with a comparison of the mental agility required for understanding political speeches or decoding a military transmission. However, comparable in mental agility does not mean equal in difficulty.
Choice C: No. This choice is out of scope. The passage provides no information to determine which array of phrases the writers of speeches might possess, nor the guidelines for using such phrases.
Choice D: Correct. This choice is supported by the passage. Politicians...attempt to communicate to each group that they are sympathetic to its cause paraphrases the last sentence of the passage, the speaker pays respect to the various concerns of his many constituents.Choice E: No. This choice is out of scope. The passage states that mental agility is required, not knowledge of rhetorical terms.
The correct answer is choice D.