What does "unreadable" indicate in radio communication?

In radio communication, the term "unreadable" specifically indicates that the message cannot be interpreted. This could be due to a variety of factors such as poor signal quality, interference, or inaudible transmission, which prevents the receiver from comprehending the content of the message. When a message is deemed unreadable, it signifies that the intended information was lost or distorted during transmission, and therefore, further attempts must be made to clarify or resend the information.

In contrast, the other options imply different conditions surrounding message clarity or urgency. For instance, stating that the message is understood would contradict the meaning of "unreadable," while indicating that the message was transmitted incorrectly suggests that there was a fault in the broadcasting process, which doesn't necessarily align with the term "unreadable." Similarly, describing a message as urgent does not relate to its clarity or intelligibility; rather, it focuses on the importance or immediacy of the information being communicated.