Which message variable is NOT influenced during communication effectiveness?

The correct choice underscores that the message code is not typically influenced during the communication effectiveness. The message code refers to the symbols, language, or signs used to convey information. While the selection of code can affect how clearly a message is understood, once a message is coded, its influence on the effectiveness of communication is relatively static compared to other variables.

In contrast, message content can significantly impact effectiveness because the information provided must be relevant, accurate, and tailored to the audience's needs. Similarly, the extension agent's contact, or their relationship and interaction with the audience, plays a crucial role in establishing trust and enhancing the receptiveness of the message. Lastly, the structure of a message—how it is organized and presented—also affects how well it can be understood and retained by the audience. Collectively, these elements are dynamic and can be adjusted or improved to enhance communication outcomes, while the message code remains fixed once established.