What does the light characteristic "Fl(2+1)" indicate?

The light characteristic "Fl(2+1)" indicates that a light flashes in groups, with a specified number of flashes in each group. Specifically, this means there is a pattern of two flashes followed by a single flash, creating a rhythmic signal that can be easily identified. This type of characteristic is designed to help mariners distinguish one navigational aid from another, based on the unique sequence of flashes.

The inclusion of "2+1" in the characteristic clarifies how the light behaves rhythmically, and this pattern is crucial for navigation, as it allows for immediate recognition of the light's signal against others in the vicinity. This is particularly useful in conditions where visibility might be constrained, helping vessels locate safe passages or hazards.

The other options do not accurately describe the way "Fl(2+1)" functions, as they focus on different behaviors of light characteristics, such as combining fixed lights with flashing ones or describing a continuous pattern without distinct grouping. Understanding these classifications is important for effectively interpreting and responding to navigational signals at sea.