Which piece of required GMDSS equipment is the primary source of transmitting locating signals?

Correct Answer: Option B — An EPIRB transmitting on 406 MHz.

A 406 MHz satellite EPIRB serves as the primary GMDSS source for transmitting distress and locating signals globally, interfacing with COSPAS-SARSAT satellites and incorporating a 121.5 MHz homing transmitter for final on-scene visual and electronic search.