Write the correct preposition.

The Master is  overall command of the ship, responsible   the safety  the ship and all on board. The Master can be identified by epaulettes, worn on the shoulders. To become a Master, one must have considerable seagoing experience, have passed examinations, and be fully familiarized  the ship.

The Chief Engineer is the head of the engine room. The engine room not only contains main engines which drive the propellers, but also diesel generators to supply electricity all the onboard services.