What is the exception to the requirement to show lights from sunset to sunrise?

The correct answer highlights that an oil rig is required to display lights from a specific timeframe, which is 15 minutes before sunset until sunrise. This timing is essential because it ensures the presence of the oil rig is clearly marked and visible to other vessels in the area, thereby enhancing safety and avoiding potential collisions. Oil rigs, due to their fixed position and operational nature, have specific lights designated under COLREGs (International Regulations for Preventing Collisions at Sea) that need to be visible to ensure the awareness of nearby navigation.

The other choices reference different situations. While fishing vessels often display specific lights due to their operational needs, the notion that they can turn off lights after sunset does not align with the overarching safety regulations intended to prevent collisions, making that choice incorrect. Similarly, commercial ships are bound by regulations that typically require them to show lights at all times, irrespective of weather conditions. The idea that all vessels must show lights at all times under all circumstances is a strong principle of maritime navigation, further underscoring the importance of safety on the water.