You are presented with the question "What aspect is different for Bird and fish hearts" and the following answer choices: 
- circulatory systems
 - matter vibrating
 - tissue
 - it keeps an organism warm
 - members of their own species
 - heat produced
 - blood
 - type of organs

Now knowing that fish have a circulatory system with a two-chambered heart and birds also have four-chambered hearts, choose the best answer.


 

 circulatory systems        