Why would an author choose to employ a flashback to interrupt the chronological order of a narrative? to make the story more interesting to provide background information on something important to allow the audience a break from the monotony of the normal story telling device to jump around and make a story confusing

While all the answers have a degree of validity, option C is the most correct one. Flashbacks are essentially a narrative technique that allows the author to break the usual monotony of storytelling by jumping back and forth between events and turning a linear story (from point A to point B) into a circular one (from point B to point C through point A, for instance).