The correct option is D All of these
Taxonomy deals with the study of principles and procedures of identification, nomenclature and classification. Essential features that forms the basis of modern taxonomic studies are ecological information of organisms, embryology (development processes), external and internal structure.
Ecological information of organisms means ecological relationship in which they interact with one another and with their physical environment.
Development process means embryology. It is a process by which the embryo forms and develops.
External structure deals with morphological characters and internal structure deals with anatomical character, which gives all the details of the structure of an organism including cellular structure.