4), a descriptive sentence for an image must contain at minimum: 1) the important objects (Nouns) that participate in the image, 2) Some description of the actions (Verbs) associated with these objects, 3) the scene where this image was taken and 4) the preposition that relates the objects to the scene.
a quadruplet of T = {n, v, s, p} (Noun-Verb-Scene-Preposition) that represents the core sentence structure.