4C理论中的“4C”是指() A: Coster B: Cost C: Convenience D: Communication E: Comsumer

Benjamin Davis, Jr. was ______. A: one of black fighter pilots during World War Ⅰ B: commander of a group of black fighter pilots during World War Ⅱ C: one of the soldiers who crossed the Delaware with Washington in 1776 D: a scout for Coster and died at the Little Big Horn