The correct answer is C. FORMAT A: /S.
The FORMAT command formats a floppy disk. The /S switch tells FORMAT to transfer the system files to the floppy disk. The system files are necessary to boot a computer from the floppy disk.
Option A, SYS C: A:, copies the system files from the hard drive to the floppy disk. However, it does not format the floppy disk.
Option B, SYS A:, copies the system files from the floppy disk to the hard drive. However, it does not format the floppy disk.
Option D, FORMAT A: /T, formats the floppy disk with a specific track and sector layout. This option is not necessary to transfer the system files.
Option E, None of the above, is incorrect.