Which of the following is an example of a secondary memory device ?

Secondary memory refers to non-volatile storage devices that retain data even when the power is turned off, unlike primary memory which is volatile and loses data without power. A Hard Disk (Option C) is a classic example of secondary memory because it stores data permanently for long-term use, such as operating systems, applications, and user files. In contrast, RAM (Option A) is volatile primary memory used for temporary data processing while the computer is running. Cache memory (Option B) and Registers (Option D) are also types of primary memory located closer to the CPU for high-speed access but do not retain data after shutdown. Therefore, since a Hard Disk provides permanent storage independent of power, it is the correct example of secondary memory.