Which of the following is classified as an output device that retrieves information from the hard disk?

The monitor is classified as an output device because its primary function is to display information generated by the computer. When you retrieve data from the hard disk, that information is processed and sent to the monitor, allowing you to view it visually. Essentially, the monitor translates the digital signals from the computer into a form (graphics, text, etc.) that we can see, making it a crucial component in how we interact with our digital information.

Other devices listed serve different functions; for instance, a keyboard is primarily an input device used to enter data into the computer. A scanner is also an input device but is used to digitize physical documents. A router, on the other hand, facilitates communication between different networks and devices but does not display or retrieve information directly from the hard disk. Thus, the monitor stands out as the correct answer since it is specifically designed to output data received from storage drives.