The Following Questions Refer to the Painting Below

The following questions refer to the painting below.

Library of Congress Prints and Photographs Division Washington,D.C[LC-USZC4-3246]
Thomas Moran,Tower Falls and Sulphur Mountain,Yellowstone,1875
-American expansion and settlement in the region depicted here was initially sparked by

A) the defeat of the remaining American Indian tribes in the area.
B) the completion of the transcontinental railroad.
C) the discovery of mineral resources.
D) government subsidies for settlers willing to farm.