Characteristics of class Reptilia are as follows:
1) Hard, horny scaly skin, four legs and breathe with lungs.
2) Three-chambered heart (crocodiles have a four-chambered heart), breathe through lungs, cold-blooded or poikilothermic.
3) Eggs have a leathery shell.
4) Unisexual, oviparous, fertilization is internal.
5) For example, turtle, chameleon, snakes, lizards etc.
So, the correct answer is option D.