Lewis and Clark traveled from St. Louis, which is beside the Mississippi River. Which of the following correctly describes the land they saw as they traveled to the Pacific Northwest?

Flat and low around the Mississippi River, with a sharp and sudden rise to the Rocky Mountains, tapering off slowly to the ocean

Flat and low around the Mississipi River, gradually rising to the Rocky Mountains, then tapering off quickly to the ocean

Flat but high around the Mississippi River, with a sharp and sudden rise to the Rocky Mountains, dropping off suddenly to the ocean

Flat but high around the Mississippi River, quickly rising to the Rocky Mountains, then tapering off slowly to the ocean