You are presented with the question "What has a relatively complex circulatory system with a three-chambered heart?" and the following answer choices: 
- sharks
 - pan
 - frogs
 - Man
 - Birds
 - alpacas
 - salmon
 - a fish

Now knowing that amphibians have a relatively complex circulatory system with a three-chambered heart and all frogs are amphibians, choose the best answer.


 

   frogs      