The correct answer is - c. east.
The Appalachian Mountains are located in the eastern part of the United States, and since the Rocky Mountains are in the western part of the country, it puts them east of the Rocky Mountains.
The Appalachians are a very old mountain range, they are dated to about 480 million years ago when they formed during the Ordovician Period. At their peak, these mountains reached heights similar to the Rocky Mountains and the Alps in Europe, but because of the natural erosion they have shrunk and nowadays are much smaller in height.
