Which one is the most striking or common character of the vertebrates?

Why do we classify both snakes and turtles in the same class?

Classify the following organisms based on the presence of a true coelom: $Spongilla$,$Planaria$,$Scorpion$,$Birds$,$Ascaris$,$Nereis$.

Which one is a true fish?

Name the phylum to which Leech and Earthworm belong.

Classify the following organisms based on the absence $/$ presence of true coelom,i.e.,acoelomate,pseudocoelomate,and coelomate:
$(a)$ Scorpion
$(b)$ Sea anemone
$(c)$ Ascaris
$(d)$ Earthworm
$(e)$ Wuchereria
$(f)$ Nereis