Final answer:
File system fragmentation refers to the non-contiguous storage of used space on a device, which can slow down system performance.
Step-by-step explanation:
File system fragmentation occurs when used space is not contiguous on a storage device. When a file system is fragmented, pieces of files, or the files themselves, are spread out across the disk rather than being stored in a single, continuous area. This can lead to slower access times as the read/write head of the disk must move to different areas to access the complete file. The correct option that defines file system fragmentation is b) used space is not contiguous. Over time, as files are created, modified, and deleted, fragmentation tends to increase, which can impact system performance. To resolve this, a process called defragmentation can be used, which rearranges the files on the disk to occupy contiguous storage locations, thereby improving access times and system efficiency.