Final answer:
Swapping in computer systems requires a backing store, which is an area on a hard drive or solid-state drive used by the operating system to free up RAM for new tasks by temporarily storing data.
Step-by-step explanation:
Swapping requires a backing store. The correct answer is d) Backing store. Swapping is a process used by operating systems to manage memory usage. When the physical RAM is full, and the operating system needs to execute another program, it will swap out some data from the RAM to a designated area of the hard drive, which is referred to as the backing store. This allows the system to free up RAM for new tasks while ensuring that the swapped out data can be retrieved later if needed. The backing store is typically part of the hard disk or a solid-state drive, which is significantly slower than RAM, but can hold much more data.