Which of the following input devices is operated using a stylus?

A digitizer is specifically designed to convert handwritten or drawn input into digital data, and it is commonly operated using a stylus. This device allows users to interact with graphics directly, making it especially popular for artistic applications, graphic design, and precise data entry. The stylus provides a level of precision and control that is ideal for tasks such as drawing or writing, which is a distinct advantage over other input devices that do not offer this direct interaction.

In contrast, a scanner is used to capture images or documents and does not require a stylus for operation; it relies on scanning techniques to digitize physical items. A keyboard is designed for typing text and interacting with computers through key presses, rather than fine drawing or writing inputs. Similarly, a mouse is a pointing device that allows users to navigate a graphical user interface but does not use a stylus. Thus, the digitizer stands out as the unique choice that specifically employs a stylus for its intended function.