Answer is: A. Genus and species.
Carl Linnaeus (1707–1778) was a Swedish botanist, physician and zoologis.
Linnaeus discovered binomial nomenclature (system of naming organisms).
Binomial nomenclature or binary nomenclature is a formal system of naming species composed of two parts.
The first part of the species name identifies the genus and the second part identifies the species within the genus.
For example, Cornu aspersum is garden snail.