Which detail from the passage helps to develop the idea that many Americans are unaware of the greatness of the nation's national parks?

A.
Most of these places are located in remote areas, with two outside the United States.
B.
Yellowstone is among the most populated wildlife areas in the world, with few humans.
C.
Tourism to these places did not build until after Congress set them apart as parks.
D.
Until recently there were no roads, trails, hotels, or camps in any of the national parks.