In "An Army Corps Like No Other," why does the author mention that Major George H. Crossman was a "skilled explorer" of the Southwest? A) to show that he spent his entire childhood in the Southwest, raising camels to sell at his local market

B) to explain his connection to the newly built railroads in the region

C) to criticize his research methods in exploring the Southwest

D) to give him credibility as someone who may understand that the Southwest would be a great place for camels