Crowbar Records used to sell its music CDs through a network of retail outlets, record stores, and music dealers but stopped using these agents with the advent of MP3 technology. Crowbar now sells its music independently on its Web site, through personal mail, and on social networking sites. Which type of marketing system has Crowbar most likely adopted?
A) an administered marketing system
B) a contractual marketing system
C) a horizontal marketing channel
D) a direct marketing channel
E) a vertical marketing channel
Answer: D) a direct marketing channel