he word "book" is a noun because it represents a physical object or thing. A noun is a word that names a person, place, thing, or idea. "Placed" is a verb indicating an action, "on" is a preposition showing position, and "is" is a helping verb. Another noun in the sentence is "table," but since the question asks for one noun, "book" is the correct choice. Identifying nouns correctly helps improve writing and communication skills.