What are the three main career fields in Merchant Marines training?

The correct grouping that outlines the three main career fields in Merchant Marines training is deck, engineering, and service.

Deck involves navigation and ship operations. Individuals in this field are trained in managing the ship's voyage, cargo handling, and ensuring the safety of the vessel.

Engineering focuses on the technical operation and maintenance of the ship’s engine and machinery. Those trained in this area are essential for the propulsion and operational efficiency of the vessel.

Service encompasses various support roles, including those involved in the overall management and logistical operations of the ship, ensuring that all aspects of the crew's needs and the ship's functionality are met.

This breakdown of the Merchant Marine career fields provides a comprehensive understanding of the training pathways available for individuals pursuing careers in this sector. The other groupings mentioned do not accurately reflect the core areas of training recognized in the Merchant Marine structure.