The protagonist of a story can be identified by looking for certain qualities such as their primary goal, the choices they make, and the emotions they evoke in the reader. It's also important to look for character development over the course of the story, as the protagonist should typically undergo some kind of transformation or growth. Additionally, it may be useful to consider how the protagonist interacts with other characters in the story, and how the other characters view and react to the protagonist. Ultimately, by looking for these elements in the story, you can determine who the protagonist is.