Which element of an epic poem features a call for divine aid? in medias res

an invocation

an extended simile

a famous battle

The correct answer is an invocation.

The root of the word invocation is voice, which means that you are calling someone to join you. That is exactly what invocation is - summoning someone divine to aid you, especially in Greek epic poems.

In medias res means that the story begins immediately, without any introduction; an extended simile is when you compare two or more things, but the comparison takes place over several lines.

The correct answer is an invocation

In medias res is when a story begins without a specific introduction, an extended simile is a comparison, while a famous battle is a famous battle. Invocation is summoning divine aid.