What type of storage is characterized as non-volatile and cannot be accessed once removed?

The characteristic of being non-volatile means that the data stored retains its value even when the power is turned off. ROM, or Read-Only Memory, fits this description as it is designed to store firmware or software that is not intended to be modified frequently. When ROM is removed from a device, the data it contains is inaccessible; this is a key feature that differentiates it from other types of storage.

In contrast, RAM (Random Access Memory) is volatile, meaning it loses all stored data when power is lost, which rules it out. Optical technologies, like CDs or DVDs, are also removable and do allow access when outside their devices, eliminating them as well. SSDs (Solid State Drives) are non-volatile too but can be accessed after removal, showcasing the importance of the "cannot be accessed once removed" aspect in identifying the correct answer. Thus, the defining attributes of ROM align perfectly with the criteria given in the question.