By 1860, then, war was inevitable. Naturally, the conflict would at once present intricate military problems, and among them the retention of the Pacific Coast was of the deepest concern to the Union. Situated at a distance of nearly two thousand miles from the Missouri River which was then the nation's western frontier, this intervening space comprised trackless plains, almost impenetrable ranges of snow-capped mountains, and parched alkali deserts. And besides these barriers of nature which lay between the West coast and the settled eastern half of the country, there were many fierce tribes of savages who were usually on the alert to oppose the movements of the white race through their dominions.

In this excerpt from "The Pony Express" chapter one, the physical description of the land between the Pacific Coast and the Missouri River tells the reader the area was

A. picturesque and lovely to see

B. dangerous and difficult to travel

C. interesting and fascinating to study

D. confusing and difficult to understand