Which of the following states is NOT within the Mountain Plains Region?

D is correct because Ohio is located in the Midwestern Region of the United States and is situated to the east of the Mountain Plains Region. The Mountain Plains Region typically includes states that are geographically positioned in the central part of the country, specifically those that lie within or adjacent to the Rocky Mountain range.

Kansas, Texas, and Oklahoma are all part of the Mountain Plains Region, as they are situated further west and north compared to Ohio, making them characteristics of this specific geographic area. Kansas and Oklahoma are directly in the plains, while Texas, while larger and extending into various regions, includes parts that fit within the Mountain Plains description.