Concept:A stylus pen is a digital input tool used to draw or write freely on screens.Explanation:Freehand drawing on digital devices requires a tool that can move smoothly like a pen or pencil.A stylus pen is commonly used on tablets and touchscreens for this purpose.Ball pin and drawing pin are not digital tools.A graphic table is not as direct a drawing tool as a stylus pen.Answer:D. Stylus pen