The correct answer is A) Shut down any cargo transfer that's in progress. This is the correct answer because in an emergency situation where the vessel's stern is falling away from the dock, the immediate priority is to stop any ongoing cargo transfer. This ensures the safety of the cargo operations and prevents any potential spills or other hazardous incidents. Shutting down the cargo transfer should be the first step before taking any other measures to secure the vessel. The other options, while potentially useful, are not the immediate first step that should be taken. Obtaining assistance from the terminal, notifying the engine room, or letting go the anchor would all be subsequent actions once the cargo transfer has been stopped.