Most isolationists felt that there was no need for americans to feel threatened by developments in Europe and Asia because the vast pacific and atlantic oceans insulated the country from troubles in those regions, and the United States had formed friendly alliances with all the other nations in the Western hemisphere.
The opposite sum of a number refers to the fact that the opposite of a sum of real numbers is equal to the sum of the opposite. Base on that, the answer would be letter D. -(-17+5) = 17+(-5). I hope you are satisfied with my answer and feel free to ask for more
