Pre-Civil War pioneers crossed the Great Plains with no intention of s

Pre-Civil War pioneers crossed the Great Plains with no intention of stopping there to start a settlement.

The post-Civil War pioneers were intentionally moving to the Great Plains. What events made this area attractive?
A) the passing of the Homestead Act, the ability to farm, and the discovery of mineral wealth
B) the Homestead Act, the absence of tribal unrest, and the discovery of gold
C) the Dawes Act, the Homestead Act, and the discovery of gold
D) the peace between the Native Americans and the U.S. Army, the discovery of gold, and the ability to farm

ANSWER
Answer: A