Explanation: In Digital Selective Calling (DSC) messages, ECC stands for **Error Check Character**. This is a critical component for ensuring the reliability of digital transmissions over potentially noisy radio channels. Before a DSC message is transmitted, a specific algorithm calculates an ECC based on all the other data characters within the message. This calculated ECC is then appended to the message. Upon reception, the receiving radio performs the *same* calculation on the received data characters. If the newly calculated ECC matches the ECC character received with the message, it indicates that the message was likely received without errors. If they don't match, an error is detected, and the message might be rejected or flagged. This process, a fundamental aspect of digital radio communication theory, ensures the integrity and accuracy of vital information like distress alerts. Options B, C, and D are not standard terms related to error detection in digital communication.