Final answer:
The Rocky Mountains extend from Canada down to New Mexico. They have undergone significant natural changes over millions of years, contributing to their current appearance and geographic extent. The correct answer is C.
Step-by-step explanation:
The Rocky Mountains extend from Canada to New Mexico. This mountain range, which started forming over 80 million years ago, has experienced significant glaciation and erosion leading to its current shape. The Spine of the Continent Wildway extends from Alaska through the Mountain West, including the southern portion of the Canadian Rockies, down to the uplands of Western Mexico, indicating the continued geographic presence of these mountains in North America. The correct answer is C.