Which parameter influences the Required Subdivision Index "R" for passenger ships?

The Required Subdivision Index "R" for passenger ships is primarily influenced by factors that relate to the safety and survivability of large numbers of people on board. The number of persons onboard plays a crucial role, as a higher number of passengers increases the potential risk in the event of a marine accident. This means that regulatory bodies require a higher subdivision index, which directly correlates to hull design and safety features needed to ensure safety in emergencies.

Additionally, the length of the ship is an important factor because it affects the ship's stability and hydrodynamic behavior. Longer ships may require different design strategies to enhance their safety and structural integrity as they operate in various sea conditions. This intertwining of passenger capacity and ship length makes option C the most accurate choice, as both parameters directly impact the required safety measures and classification standards that the ship must comply with to protect passengers effectively.