The correct answer is C. Backing store.
Backing store is any storage device added to a computer beyond the immediately usable main storage. It is used to store data that is not currently being used by the computer, but may be needed later. Backing store can be used to store programs, data files, and other information.
A floppy disk is a portable, removable data storage medium that was widely used from the 1970s to the early 2000s. Floppy disks were typically used to store computer programs and data files.
A hard disk is a non-volatile data storage device that is used for storing and retrieving digital information. Hard disks are typically used as the primary storage device in personal computers and workstations.
A punched card is a piece of stiff paper with rectangular holes punched into it. Punched cards were used as a data storage medium for early computers.
E is not the correct answer because it is not a type of storage device.