Final answer:
The author creates an effective appeal to logic (logos) by encouraging a cost comparison between maintaining old levees and building new ones, focusing on credible evidence and logical reasoning. The correct answer is option: D. encouraging readers to compare the cost of maintaining old levees with thecost of building new ones.
Step-by-step explanation:
One way the author creates an effective appeal to logic in support of his or her claim is by encouraging readers to compare the cost of maintaining old levees with the cost of building new ones. This approach directly appeals to logical reasoning and the audience's rational thought process, by presenting a clear, pragmatic comparison that uses credible evidence and real-world implications to back up the author's position. It avoids the pitfalls of emotional manipulation, irrelevant attacks, or unfounded assumptions, which are less effective in appealing to an audience's logic.