Answer: C. Allusion; the phrase goat-footed connects balloon man to the Greek god pan, who heralded the coming of spring.
An allusion is a figure of speech in which a character, event or object from a different context is referred to indirectly, hoping that the audience would be able to make the direct connection. Therefore, allusions usually reference well-known works of art, myths, folk tales, historical events, etc. that would be familar to most readers. In this case, the reference to a "goat-footed" being refers to the Greek god Pan.