The correct answer is 3) To understand an author’s full intent.
Indeed, literary authors use figurative language in order to infuse their text with more intense emotional charge and more complex meaning. For that purpose, several figures of speech are used. A metaphor is the classic exampla of figurative speech. A good example is the foloowing:
“Masked, I advance.” Rene Descartes.
Descartes does not literally wear a mask but he uses one figuratively in order to reveal his true self. In literal language the words would be: “ I show an alternative persona in my social interactions who is more akin to who I really am.”