According to the Text,the Confusion Over the Definition of the Marketing

According to the text,the confusion over the definition of the marketing channel stems mainly from which of the following causes?

A) Marketing channels are complex.
B) There are simply too many definitions of the marketing channel.
C) Too many "academic types" have become involved.
D) The differing perspectives or viewpoints used.
E) There are too many marketing channels for anyone to understand.