Which of the following devices cannot permanently store data?

The monitor is a display device that presents visual output from a computer system but does not have any capability to store data permanently. It functions primarily to show information generated by the CPU and other components but relies entirely on external sources of information, like RAM or secondary storage devices, for the data it displays. Data is not retained on a monitor once it is turned off or loses power; it requires a constant input signal to show information.

In contrast, the central processing unit (CPU) processes data and executes instructions but does not have the capacity to store data permanently. Other options, such as CD-ROMs and hard disks, are specifically designed for data storage. CD-ROMs can hold data for long periods, and hard disks are designed for both short-term and long-term storage, providing a persistent way to retain information even when the system is powered down. Therefore, the monitor stands out as the device that does not offer any form of permanent data storage.