Why ARQ stands for Automatic Repeat reQuest. The receiver checks each received block against a checksum or CRC, and if the block fails the check, the receiver sends a NAK (or withholds the ACK) so the sender transmits that block again. This is error detection plus retransmission, not true forward error correction, so it needs a reliable return path and works best on links where the sender can hear the receiver, as in packet or PACTOR.
Watch out The choices about special binary or polynomial codes describe forward error correction (FEC), where redundant bits such as Hamming, Reed-Solomon or convolutional codes let the receiver rebuild the lost data with no reply from the sender at all.
ARQ = Automatic Repeat reQuest: "say that again." FEC fixes it locally; ARQ asks for a resend.