Which one of the following is a combination of input and output device ?

In computer science, devices are typically classified as input, output, or both (combination). Among the given options:

• Monitor: While primarily an output device, a Touchscreen Monitor acts as a combination device. It provides visual output and accepts input via touch sensors. In many competitive examinations, "Monitor" is the accepted answer for a combination device when specific alternatives like "Modem" or "Touchscreen" are not listed.
• Inkjet Printer: This is an output device that produces hard copies of text and graphics. (Note: A multi-function printer is a combination, but "Inkjet" refers specifically to the printing technology).
• Webcam: This is an input device that captures video and images to be sent to a computer.
• Bar code Reader: This is an input device used to capture and read information contained in a bar code.

Therefore, the monitor is the only device in this list that commonly exists in a form (touchscreen) that functions as both an input and output interface.