How are paired NBDP frequencies normally used?

Correct Answer: Option B — These are normally used for ARQ communications with coast radio stations.

Paired frequencies are used for ARQ (Automatic Repeat Request) mode in NBDP communications. ARQ is a synchronous, error-correcting protocol that requires a two-way link between the ship and the coast station to confirm receipt of data packets, making paired channels essential for reliable, error-free message exchange with public coast stations.