A Good Reason for Developing or Joining a Vertical Marketing

A good reason for developing or joining a vertical marketing system is that

A) the whole channel focuses on the same target market at the end of the channel and seems to be more effective.
B) market competition at each level of the channel eliminates inefficient firms and serves consumers' needs better.
C) no member of the channel has to bear the costs of the regrouping activities.
D) no member of the channel has to plan for the whole channel,since good decisions at each level run the channel.
E) All of these are good reasons for developing or joining a vertical marketing system.