What does the FAT indicate about a cluster marked with a value of 0?

A cluster marked with a value of 0 in the File Allocation Table (FAT) indicates that the cluster is unallocated. This means that the cluster is not currently assigned to any file and does not contain any data. In FAT file systems, clusters can be in various states, and a value of 0 effectively communicates that the cluster is free for use and can potentially be allocated to a new file or used for data storage when needed.

The other options reflect different conditions that clusters might be in, but they do not accurately describe a cluster with a value of 0. For instance, a cluster containing data would have a non-zero value indicating its association with a specific file. Fragmentation refers to the spread of a file across multiple clusters, which would not apply to an unallocated cluster. Corruption implies some level of damage or error that affects the data integrity, which is not determined solely by the cluster's value in the FAT as 0 suggests it is simply free.