Scientists use a system called Classification of Living Things, which categorizes each living organism into the following groups: Kingdom, Phylum, Class, Order, Family, Genus, and Species.
Habitat, place where an organism or a community of organisms lives, including all living and nonliving factors or conditions of the surrounding environment. A host organism inhabited by parasites is as much a habitat as a terrestrial place such as a grove of trees or an aquatic locality such as a small pond.
I think the answer is C. Genetic variation
