Final answer:
The Rocky Mountains are located in the western region of the United States, forming part of the larger Mountain West and stretching from New Mexico to northern Canada.
Therefore, the correct answer is: option D) West
Step-by-step explanation:
The Rocky Mountains formed between 80 million to 55 million years ago during the Laramide Orogeny, an event of large-scale deformation due to the interaction between tectonic plates.
The Rocky Mountains are located in the western region of the United States. Specifically, they extend from New Mexico all the way to northern Canada, forming a significant mountain range that is part of the larger Mountain West region, which includes not just the Rocky Mountains but also other ranges such as the Sierra Nevada, the Cascades, and various intermontane basins and plateaus.
Today, these mountains are a prominent physical feature in the West, showcasing the geological history through formations like glaciated peaks and erosion-formed landscapes.