Concept:Secondary storage devices are used to store data permanently outside the main memory of a computer.Explanation:RAM and EPROM are types of primary memory that the CPU accesses directly.Bubble memory is a non-volatile storage technology, but it is not commonly classified as a secondary storage device in standard board exam contexts.A floppy disk is a portable magnetic storage medium.It holds data externally and independently of the main memory.Therefore, it functions as a secondary storage device.Answer:C. floppy disk