Question

cnidaria - shape of life
which group of animals came before the cnidarians?
worms
sponges
mollusks
arthropods

Explanation:

Sponges (Porifera) are among the simplest and earliest - branching animal groups. Cnidarians (like jellyfish, corals) evolved after sponges. Worms (Annelids, Platyhelminthes etc.), mollusks (like snails, clams), and arthropods (insects, crustaceans) are more complex and evolved after cnidarians.

Answer:

Sponges