When you summarize, you take the main points of a story and write in in a few sentences. You want to make sure you hit all the key parts of the story and don't focus on the small details. If you were telling a friend about a movie you saw, you would by describe the major events, but not the little moments. That would be summarizing. You can do this with any book,movie,story etc. :)
D. He breaks the window so the bird can fly away
