Which two of these characteristics are common to epics and ballads both originated from the oral poetic tradition. both revolve around the exploits of a central hero. both use iambic pentameter and a simple rhyme scheme. both contain the elements of a narrative. both are exclusively focused on mythological stories.

Both originated from the oral poetic tradition. Both contain the elements of a narrative.

Process of elimination can be a helpful strategy for questions where you have more than one right answer. Let's use the Odyssey, a famous epic, as a way to eliminate some answers. The Odyssey is not written in iambic pentameter, nor does it have a rhyme scheme. It also does not exclusively focus on a mythological story. It is a narrative (story), it does originate from the oral tradition, and it does revolve around the exploits of a central hero (Odysseus). Unlike epic poetry, ballads have a rhyme scheme but do not revolve around the exploits of a central hero. For example, Poe's Annabel Lee is a ballad. It has a rhyme scheme. It focuses on the speakers love for Annabel Lee.