What led to the battle of little bighorn?

It was led by George Armstrong Custer against the Lakota Sioux and Cheyenne Warriors bc the tension between the two had risen from finding out about gold on the Native American Lands. A number of tribes missed the federal deadline to move to reservations, the U.S. Army, including Custer and his 7th Calvary, was dispatched to confront them. 

The answer is a) reside