The sequence of the one-way gaseous exchange mechanism in a fish is?
A. mouth --> operculum -> gills B. mouth -> gills > operculum C. operculum > gills -> mouth D. gills -> operculum --> mouth
Correct Answer: B
Explanation
Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills.
In some fish, capillary blood flows in the opposite direction to the water, causing counter-current exchange. The gills push the oxygen-poor water out through openings in the sides(opercula) of the pharynx.
