A file's physical size is defined as which of the following?

The answer is accurate because the physical size of a file is indeed determined by the actual disk space it occupies, which includes not only the bytes representing the actual data (the logical size) but also any additional space that may be reserved and not fully used. This includes slack space, which is found at the end of a block or cluster where data is stored. The logical size refers only to the actual bytes used by the file, while the physical size accounts for the entire allocation on the disk, including that unused space.

In terms of context, the other options do not accurately reflect the definition of physical size. For instance, stating that the physical size is always greater than the logical size would not hold in all cases, particularly if the file has been precisely allocated to fit its data without any slack. Furthermore, claiming that both options A and B are true overlooks the fact that A could be inaccurate. Therefore, the most precise and comprehensive way to define the physical size is through the description provided in option B.