Which of the following statements concerning SITOR communications is true?

Correct Answer: Option C — In ARQ, the "information sending station" will transmit a block of three characters that the receiving station will subsequently acknowledge or request be retransmitted.

ARQ mode functions by the Information Sending Station (ISS) transmitting a block of three characters. The Information Receiving Station (IRS) verifies the parity of this block and sends a control signal back to the ISS, either acknowledging receipt or requesting a retransmission if errors are detected.