The correct answer is: Distortion
Rationale: Noise is the other main type of communication problem: interferences in the environment in which communication takes place, affecting the clarity, accuracy or arrival of the message.
Redundancy is a positive principle in this context: you can use more than one form of communication, so that if one message does not get through (perhaps because of noise or distortion), another may.
Feedback is an essential part of the communication cycle: it is the response which indicates to the sender whether the message has been correctly received.
