Question

according to the cladogram, which organisms have roundworms as a common ancestor?
mollusks and flatworms
sponges and chordates
flatworms, sponges, and cnidarians
mollusks, echinoderms, chordates, and annelids

Explanation:

A cladogram shows evolutionary relationships, where groups branching off after a shared trait share the ancestor with that trait. Roundworms have the pseudocoelom trait, and all groups that branch from the node after roundworms (mollusks, annelids, arthropods, echinoderms, chordates) share roundworms as a common ancestor. The other options include groups that branch before roundworms (sponges, cnidarians, flatworms) and do not share this ancestor.

Answer:

D. mollusks, echinoderms, chordates, and annelids