Built mounds between 1000 bc and 1000 ad to use for burial and religious ceremonies

What makes fort sill historically unique among other regional military installations? a. it is the site where seven major commanders of us military efforts were trained. b. it houses the largest explosive weapons factory in the united states. c. it specializes in training soldiers to preserve the cultural artifacts of nations invaded by the us military. d. it is the oldest functioning installation in oklahoma.