Answer:
The correct answer is option a. "Shared DNA sequences".
Step-by-step explanation:
The most reliable evidence that suggest that vertebrates are more closely related to echinoderms than are any other invertebrate phyla is the fact that vertebrates share DNA sequences with echinoderms. Among the different genes that have been analyzed between vertebrates and echinoderms, the genes involved in immunology and biomineralization are the ones practically identical among these two categories of species.