Which light arrangement is used for vessels constrained by draft?

The arrangement of lights that is used for vessels constrained by draft is signified by three red lights and a stern light. This setup is applicable to vessels that cannot navigate safely in shallow waters due to their draft. The three red lights are displayed vertically, indicating that the vessel is constrained by its draft, while the stern light provides additional visibility to other vessels in the area.

This specific configuration is vital for ensuring safety in maritime navigation, as it communicates to nearby vessels the limitations of the ship's movement and the potential hazards involved. Visibility of these lights allows other vessels to take appropriate action to avoid collision and understand the navigation constraints of the vessel in question.

The other options, while related to different types of vessels and their signaling systems, do not apply to vessels constrained by draft. Each of those combinations of lights serves different purposes and indicates various conditions or constraints in maritime navigation.