4.vertebrates are diveded into five classes namely: a.insects,arachnids,birds,fishes,crustaceans b.cnidarians,cantipede,mammals,reptiles,fishes c.millipedes,insects.bird,reptiles,arachnids d.mammals,reptiles,amphibians,fishes,birds
Because the letters A, B, and C, Though they may contain a mammal and vertebrate kind in the list, most of them also contain inverterbrates like the cnidarian, insects, etc. While letter D contains all mammals that are all vertebrates.
