Which device cannot permanently store data?

The device that cannot permanently store data is the monitor. A monitor is designed to display visual information generated by a computer but does not have the capability to retain or store data. It functions as an output device, delivering images and information to users but does not have any memory or storage components that would allow it to save data over time.

In contrast, CD-ROMs and hard disks are designed specifically for data storage. A CD-ROM can retain information until it is physically damaged or the disc is no longer readable. Hard disks are intended for long-term data storage, effectively keeping data intact even when the power is turned off, as they utilize magnetic storage technology. The CPU, or Central Processing Unit, while responsible for processing data, does not store information permanently either; it operates with data stored in RAM and must rely on other storage devices to retain information beyond the immediate processing.

Therefore, highlighting the differences in functionality clarifies why the monitor is the only option that lacks the capability to store data permanently.