Answer:
The correct answer is all chordates.
Step-by-step explanation:
The individual opening of gills are called gill slits.Many organism such as fish and sharks which belongs to chordates family have gill slits.
Gill slits helps in the filtration of food particle from water.Beside this gill slits helps in proper respiration or respiratory exchange of oxygen and carbon dioxide gas.
Gill slits creates a connection with pharynx and this connection helps in the passage of water to the exterior,thereby helps in the wetting of gills.Fishes and sharks contain gills during the embryonic stage of their development.