Final answer:
In forensic analysis, a FAT system retains data from previous allocations in the clusters marked as free, which is useful for data recovery and forensic purposes until overwritten by new data.
Correct option is C. retain data from previous allocations and are very useful therefore.
Step-by-step explanation:
In the context of forensic analysis of a File Allocation Table (FAT) system, the correct answer is C. In a FAT system, clusters of data which are marked as free (i.e., 'deleted' by the system) do indeed retain data from previous allocations. This is because when a file is deleted in a FAT system, the operating system only changes the status of the data clusters as available for new data, but does not actually overwrite the existing data immediately.
Consequently, unless new data is written to those clusters, the original data remains intact and can be very useful for forensic purposes. For example, forensic analysts can often recover deleted files or fragments of files which can provide critical information in an investigation.