Selective FEC communications (SFEC) are employed when:

Correct Answer: Option C — An individual station must receive communications without using any transmitters (Radio Silence).

Selective FEC (SFEC) allows a coast station to send a message to a specific vessel without requiring that vessel to transmit. This is essential during periods of radio silence or when the receiving vessel's transmitter is inoperative, as the receiver synchronizes to the broadcast using the sender's signal.