I asked that question too
D. It joined the Confederacy and became the 12th state to secede from the Union, West Virginia
<span>provoked by a treaty-violating ultimatum to surrender their sacred Black Hills (Paha Sapa), where an expedition under Custer discovered gold in 1874. In June 1876, driven by converging army columns, a unique concentration of Sioux and Cheyenne/Arapaho in southern Montana first repulsed a 1, 000-man column under Crook at the Rosebud and then destroyed Custer's command at Little Bighorn. </span>