There has been an increase in the number of chambers in the heart during the evolution of vertebrates. Name the classes of vertebrates that have two,three,and four-chambered hearts.

(N/A) Two-chambered heart: Present in fishes. It consists of one atrium and one ventricle,where oxygenated and deoxygenated blood mix.
$(b)$ Three-chambered heart: Present in amphibians. The atrium is divided into right and left halves,but the ventricle is undivided,leading to the mixing of blood.
$(c)$ Incomplete four-chambered heart: Present in most reptiles (except crocodiles). The ventricle is partially divided by an incomplete septum.
$(d)$ Four-chambered heart: Present in birds,mammals,and crocodiles. Both atria and ventricles are completely divided,preventing the mixing of oxygenated and deoxygenated blood.