You are presented with the question "The two-chambered heart of some backboned aquatic animals is part of their:" and the following answer choices: 
- aerobic capacity
 - three-chambered heart
 - biological diversity
 - it keeps an organism warm
 - the body's largest organ
 - circulatory system
 - salmon
 - swimming system

Now knowing that fish have a circulatory system with a two-chambered heart and fish are backboned aquatic animals, choose the best answer.


 

      circulatory system   