DETROIT - General Motor's (NYSE: GM) Chevrolet, Buick, GMC and Cadillac brands sold 272,512 vehicles in the United States in July 2015, a 6 percent increase and the four brands' best combined July since 2007.
In the context of the input sentence, determine the relationship between 'GMC' and 'DETROIT'.
Options: distributed by, creator, headquarters location, stock exchange