Answer : 3. "पानी से घुलनशील ऑक्सीजन को अवशोषित करें"
Explanation :

Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers (operculum) on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments.