The correct answer is - C. the Rio Grande.
The United States and Canada share multiple geographical features, including the Great Lakes, the Great Plains, and the Rocky Mountains, but the Rio Grande River is not one of those that are shared between these two vast countries.
The Rio Grande is a river that is actually shared by the United States and Mexico. This river starts its flow in Colorado, continuing in New Mexico, forming a little bit of the federal border between New Mexico and Texas, and than forming the whole US-Mexico border (between Texas and Mexico, not all of it). The river ends its flow in the Gulf of Mexico.
