I believe the answer is: Devon is the sender and Carol is the receiver. Her facial expressions are encoded message
Encoded message refers to the process that is being made to our message in order to make it more easily understood. This could be done by accompanying the message with facial expression to highlight the emotion that we felt about the content of the message.
Devon is having a conversation with carol. As Devon speaks to carol, she crosses her arms and looks perturbed. Devon notices that carol looks unhappy and begins to talk about something else. When Devon changes topics, carol wonders why the conversation shifted and looks confused. From what is described here, Devon is the sender and Carol is the receiver, as her facial expressions are an encoded message.
