Which of the following lists devices that are typically considered secondary storage?

• A. RAM and cache
• B. CPU registers
• C. SSD performance metrics
• D. HDDs, SSDs, CDs and SD cards

Answer: (D)

Secondary storage refers to non-volatile storage devices that hold data outside the system’s active working memory. These devices retain information even when the power is off, usually offering larger capacity but slower access compared to main memory. Typical examples include HDDs and SSDs for long-term data storage, as well as optical media like CDs and removable flash options such as SD cards. These are the kinds of devices used to keep data, programs, and files for extended periods.

In contrast, RAM and cache are primary storage: fast, volatile memory that the CPU uses during active computation and that loses contents when power is removed. CPU registers are also primary storage, extremely fast, but very small. SSD performance metrics describe how well a device performs rather than identifying a type of storage device, so they don’t form a list of storage devices themselves. Therefore, the list containing HDDs, SSDs, CDs, and SD cards best matches the concept of secondary storage.