Answer:
A. Exposition
Explanation:
Exposition is a literary device used to introduce background information about <em>events</em>, <em>settings</em>, <em>characters</em>, or other elements of a work to the audience or readers. ... Exposition is crucial to any story, for without it nothing makes sense.
Either a or b. I don't know the story though but good luck.
According to researchers...
because that means scientists have researched it