The correct option is
A Palaeontology
Study of fossil of animals and plants is called as palaeontology.
Herpetology is the study of amphibians like frogs, toads, salamanders and reptiles like snakes, lizards, turtles.
Saurology is the study of lizards.
Organic evolution is the process by which genetic changes occur in a population in response to environmental changes.
Thus, the correct answer is 'Palaeontology'.