Who must be present when opening the MRG and is responsible for maintaining the keys to it?

The Engineering Officer is the individual responsible for opening the Main Reduction Gear (MRG) and maintaining the keys associated with it. This is critical because the MRG is a crucial component of the ship's propulsion system, and access to it needs to be controlled and regulated to ensure operational safety and integrity. The Engineering Officer is trained and knowledgeable about the technical aspects and safety protocols associated with the gear and is typically tasked with the oversight of engineering operations, including maintenance and inspections.

The presence of the Engineering Officer during this process ensures that any potential issues are addressed by someone with the appropriate expertise. It also helps to maintain accountability for the equipment, which is vital in preventing unauthorized access that could lead to accidents or equipment failure. Other roles, while important in their own right, do not have the specific responsibility tied directly to the MRG and its access control.