Amphibians have a relatively complex circulatory system with a three-chambered heart.
Frogs have a three-chambered heart, consisting of two atria and a single ventricle.
Frogs are amphibians.
What group of animals do frogs belong to?
Options:
A: four limbs
B: animals
C: fish
D: warm-blooded
E: reptiles
F: Amphibians
G: more abundant
H: mammals