Final answer:
Apollo is the correct answer because he is traditionally seen as the son of Zeus and Leto, not Zeus and Hera. Ares and Hephaestus are usually considered the children of Zeus and Hera, while Athena is the daughter of Zeus alone.
Step-by-step explanation:
The child of Zeus and Hera that is not listed in the given options is Apollo. Apollo is traditionally seen as the son of Zeus and Leto, rather than being a child of Hera. In Greek mythology, the typical children of Zeus and Hera together include Ares (god of war) and Hephaestus (god of the forge), although there are varying accounts about Hephaestus's parentage. Some myths suggest that he was born solely from Hera without the involvement of Zeus. On the other hand, Athena (goddess of warfare and wisdom) is often recognized as the daughter of Zeus alone, having sprung fully grown and armored from his forehead. Therefore, the answer to the question is option C. Apollo, who is normally not considered a child of Zeus and Hera together.