It is sequence of the animal's DNA based on which they are classified. The animals which have more similarity in DNA sequence are considered as closely related and therefore they are classified in the same group whereas the animals which have dissimilar DNA sequence are considered as distantly located so they are classified in different groups. The structure of animal's ATP, function of the animal's limbs and composition of the animal's bones are not the criteria to classify animals.
The correct answer is letter D. The sequence of an animals' DNA is most likely the variable that scientists will look into to study it further. Knowing the genetic make-up of a particular organism is important so that they can be classified in particular groups and communities within an ecosystem.
