Bavelas, Coates, and Johnson Believe That One Reason Researchers Focus

Bavelas, Coates, and Johnson believe that one reason researchers focus greater attention on speaker roles in a conversation rather than listener roles is because

A) a listener is not necessary for someone to speak.
B) there is no message without a speaker.
C) listeners take the back channel in models of communication.
D) listening is a hypothetical construct that is difficult to measure.