The correct option is
A Classification
Taxonomy is the branch of science that deals with principles, rules and procedure of classification of organisms based on their similarities and dissimilarities.
Since, identification and nomenclature is the prerequisite for classification; the first step in taxonomy is identification followed by nomenclature and then classification.
Nomenclature refers to assign a universal scientific name to taxon based on the international rules agreed upon by ICBN/ICZN/ ICVN/ICNCP to maintain uniformity in the system.
Classification is arrangement of organisms into groups on the basis of their similarities and is preceded by identification and nomenclature. So, option A is the correct answer.