Tadpoles breathe through gills because

All frogs start life as aquatic tadpoles, breathing underwater through internal gills and their skin. Then later most develop into land animals with lungs for breathing air. But in all stages breathing is controlled by pulsing the throat. Most frogs loose their gills when they metaorphise.

... what kind of question is that! its like us... we breath through out mouth and other animals breath other ways... don't know if that helped thou

Sorry sir you did not give us the graph i typically but i'm very confused my conclusion is you're missing valuable information in the question