Which of the following devices is primarily an output device?

The monitor is primarily an output device because its main function is to display visual information and data from the computer to the user. It takes the digital signals processed by the computer and converts them into images, text, and videos that can be viewed. This represents the output of the computer’s operations, allowing users to interact with software applications, view content, and access information visually.

In contrast, the other devices listed serve different functions. A mouse and a keyboard are input devices that allow users to provide data and commands to the computer. A scanner is also an input device, as it captures and converts documents and images into digital format for the computer to process. Each of these devices plays a crucial role in computing, but the monitor distinctly serves the output function by presenting data to the user.