Amphibians have a relatively complex circulatory system with a three-chambered heart, and frogs have a three-chambered heart, consisting of two atria and a single ventricle. Given these facts, what group of animals do frogs belong to among the following options:
- four limbs
 - animals
 - fish
 - warm-blooded
 - reptiles
 - Amphibians
 - more abundant
 - mammals


 

      Amphibians   