Answer:
(a). Eukarya, Animalia, Chordata.
Step-by-step explanation:
The order of organization to classify an organism includes 7 groups from highest to lowest, which include domain, kingdom, phylum, class, order, family, and genus, and species.
Chordates are organisms, which possess a dorsal nerve cord, notochord, pharyngeal slits, and a post-anall tail, and an endostyle. These organisms belong to domain Eukarya, kingdom Animalia, and phylum Chordata.
Thus, the correct answer is option (a).