Under what conditions does the Stockholm Agreement apply?

The Stockholm Agreement specifically applies under conditions where the wave height is 4.0 meters or more, accompanied by particular freeboard requirements. This agreement was established to address safety concerns related to the operation of Roll-on/Roll-off (Ro-Ro) ferries in challenging sea conditions.

Understanding the need for this measure is crucial; as wave height increases, the risk factors associated with ferry operations also rise, including issues with vessel stability and passenger safety. The freeboard requirements that accompany this wave height threshold help ensure sufficient buoyancy and stability of the vessel when facing such conditions, aiming to mitigate the risks involved in these operational scenarios.

This context of operational safety directly connects to the intent and application of the Stockholm Agreement, making it the right answer. The other options imply conditions that do not align with the specific maritime safety objectives the agreement is designed to address.