The correct answer is D. along the Mississippi River. It is important to note that it lies on the west of the Mississippi River tallgrass prairie states and east of the Rocky Mountains in both the United States and Canada. This area is massive and most of it is covered is what is mentioned above, in prairie, steppe and grassland. It runs from Canada, all the way through a part of the United States and just stops on the border of Mexico. The Canadian provinces it goes through are: Alberta, Manitoba and Saskatchewan. In the United States, it runs through Colorado, Kansas, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, South Dakota, Texas and Wyoming. The central plains do not encompass all these states, but rather has some parts in these states.