The correct answer is D: If errors are detected, a retransmission is requested. ARQ (Automatic Repeat Request) accomplishes error correction by requesting retransmission if errors are detected. ARQ is an error control method that detects errors and requests the sender to retransmit the data. In ARQ systems, the receiver checks received data for errors (using checksums, parity, or other error detection methods). If errors are detected, the receiver sends a request (NAK - Negative Acknowledgment) back to the transmitter asking for retransmission. If no errors are detected, the receiver sends an acknowledgment (ACK). This continues until the data is received correctly. ARQ is widely used in digital communication systems because it's simple and effective, though it requires a two-way communication link.