Which one is not an output device?

The answer to this is D. A lot of people may automatically assume that the keyboard is an output device but you first have to know what the meaning of an output device is. This is a device that can provide the output that comes from the computer. An example of this is the printer. From the screen, you can print out the details that can be seen there so you will have an output.

The keyboard is an example of an input device. You will use it to place information but it cannot receive information from the other parts of the computer. Another example of an input device is the mouse. You can use it to control the actions that you will do on your computer but it will not get any data from the rest of your computer too.