Final answer:
The embryological evidence supports that chordates are most closely related to the hemichordate lineage, distinguishing them from protostomes like mollusks, annelids, and arthropods, and aligning them closer to deuterostomes, which also include echinoderms. The correct option is c.
Step-by-step explanation:
Most zoologists now believe the embryological evidence indicates the chordates have probably descended from ancestors nearest the hemichordate lineage.
The distinguishing feature in the lineage of animals is the division into protostomes and deuterostomes, and chordates fall under the latter alongside echinoderms and hemichordates. While the protostome group includes mollusks, annelids, and arthropods, this lineage diverges from that of the hemichordates and echinoderms.
Notably, the hemichordates share characteristics with chordates such as pharyngeal slits and a dorsal nerve cord, albeit not a true neural tube or a notochord, displaying a closer relationship to chordates than other invertebrate phyla.
The ecdysozoan clade, which encompasses arthropods and nematodes, represents a separate lineage distinct from the lophotrochozoan clade, to which annelids and mollusks belong. Therefore, the answer to the student's question is c. Hemichordate.