Which code can be utilized for test purposes or to check on reception?

The choice of "Receiving well" serves a specific function in communication protocols, particularly in radio and telecommunications. This code is distinctly used to indicate that the transmission has been received clearly and that there are no issues interrupting the communication. It is important during tests and checks to ensure that the signal quality is sufficient for effective communication.

In contrast, the other options do not serve the same purpose. "Busy" indicates that a line or channel is occupied and not available for further communication, which would not be useful for checking on reception. "Relay" refers to the action of passing a message on to another party but does not indicate the quality of the reception. "Transmitting too rapidly" suggests a problem that can lead to misunderstandings, as information may not be comprehensible, contradicting the objective of assessing a clear reception.

Thus, "Receiving well" is the most appropriate code for testing the clarity and reception of communication, confirming that the exchange is occurring effectively.