Fish have a circulatory system with a two-chambered heart.
Fish are backboned aquatic animals.
Some backboned aquatic animals have a circulatory system with a two-chambered heart.
The two-chambered heart of some backboned aquatic animals is part of their:

a. aerobic capacity
b. three-chambered heart
c. biological diversity
d. it keeps an organism warm
e. the body's largest organ
f. circulatory system
g. salmon
h. swimming system