Final answer:
The metaphor used by Wayne Brockriede for bilateral communication is 'Two-way street', highlighting the interactive nature of such communication.
Step-by-step explanation:
The metaphor used by Wayne Brockriede for bilateral communication is b) Two-way street. This metaphor signifies that communication is a dynamic process involving two active participants. It is an exchange where both parties contribute, listen, and respond to each other, unlike one-sided communication where only one party is actively involved.
In contrast to the metaphors of an echo chamber, where the same ideas are reflected back without change, and an unending loop, which may signify a repetitive and non-progressive dialogue, the 'two-way street' suggests progress, mutual influence, and the potential for change in understanding through communication.