Which command is used to create root directory and FAT on disk?

Answer: Option C

Format is the command used in DOS to create the root directory and File Allocation Table (FAT) on a disk.

When you format a disk using the format command, it prepares the disk by creating the necessary file system structures, including the root directory and the FAT.
The root directory is the top-level directory of a disk, where other directories and files are stored.
The FAT is a table that DOS uses to keep track of the status of each cluster on the disk (whether it is free or allocated to a file).
The syntax for formatting a disk typically involves specifying the drive letter followed by the colon (e.g., format C: for formatting the C drive).

Chkdsk is used to check the integrity of the file system and to fix errors on a disk, but it does not create the root directory or the FAT.

Command.com is the system file that contains the DOS command interpreter, not a command used for disk formatting.

Fat is not a command in DOS; it refers to the File Allocation Table itself, not a command to create it.

Therefore, the correct answer is Option C: Format.