To call another vessel for voice communications regarding important business, the GMDSS operator should:

The correct choice is based on the requirements for establishing effective voice communications under the GMDSS (Global Maritime Distress and Safety System). When calling another vessel for important business, it is essential to follow proper protocols to ensure that the communication is correctly set up and that other vessels are aware of the call.

Selecting Routine priority is appropriate for non-distress communications, which aligns with initiating contact for important business, rather than urgent or distress-related matters. Entering the vessel's MMSI (Maritime Mobile Service Identity) ensures that the communication is directed to the intended recipient. The specification of a legal alternate frequency in the transmission is vital, as it provides a fallback communication channel if the initial frequency becomes unavailable or congested.

Following these steps helps to create a structured and orderly means of communication and maintains the safety and efficiency of maritime operations. Thus, by selecting Routine priority, entering the vessel's MMSI, and designating a legal alternate frequency, the GMDSS operator sets up a protocol that adheres to best practices for maritime communication.