Fact 1: Amphibians have a relatively complex circulatory system with a three-chambered heart.

Fact 2: Frogs have a three-chambered heart, consisting of two atria and a single ventricle.

Given the two facts above, answer the question "What group of animals do frogs belong to?" with the following options: 
- four limbs
 - animals
 - fish
 - warm-blooded
 - reptiles
 - Amphibians
 - more abundant
 - mammals


 

      Amphibians   