A. they are small animals
B. they can live inside the vertebrates
C. some of them are unicellular
D. they have no backbones

Correct Answer:

Option D – they have no backbones

Explanation

– The most familiar invertebrates include the Protozoa, Porifera, Coelenterata, Platyhelminthes, Nematoda, Annelida, Echinodermata, Mollusca and Arthropoda.

– Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord.

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