Answer:
bilateral symmetry
Step-by-step explanation:
The evolutionary trait that is found in the most classes of invertebrates is bilateral symmetry. Bilateral symmetry is present in all classes of invertebrates shown on the phylogenetic tree, including mollusks, annelids, and arthropods. Radial symmetry, on the other hand, is only found in the cnidarians, and true tissues are only found in the deuterostomes. Therefore, bilateral symmetry is the trait that is found in the most classes of invertebrates.