Amphibians have a relatively complex circulatory system with a three-chambered heart.
All frogs are amphibians.
Frogs have a relatively complex circulatory system with a three-chambered heart.
what have a relatively complex circulatory system with three-chambered heart?

(a) sharks
(b) humans
(c) bacteria
(d) Birds
(e) blood
(f) frogs
(g) salmon
(h) pacemaker