Final Answer:
Insects (Option c) are not contained in phylum Chordata; they belong to the phylum Arthropoda. Phylum Chordata includes vertebrates such as fish, amphibians, and reptiles, characterized by the presence of a notochord at some stage in their development.
Step-by-step explanation:
Insects (Option c) are not part of phylum Chordata; they belong to phylum Arthropoda. Phylum Chordata encompasses a diverse group of animals characterized by the presence of a notochord at some stage in their life cycle.
This distinguishing feature is a flexible rod providing structural support. Within Chordata, there are subphyla such as Vertebrata, which includes fish, amphibians, reptiles, birds, and mammals. Insects, on the other hand, belong to the phylum Arthropoda, characterized by jointed appendages and an exoskeleton.
Despite their ecological importance and diversity, insects lack the defining chordate characteristics like a notochord. Understanding these taxonomic distinctions is fundamental in elucidating the evolutionary relationships and biological diversity present in the animal kingdom. So the correct option is C.