The correct answer is D. Diskcopy can be used with a floppy and a hard disk.
Diskcopy is a DOS command that can be used to copy the contents of one floppy disk to another floppy disk or to a hard disk. It can also be used to create a bootable floppy disk.
Copy is a DOS command that can be used to copy files from one disk to another. It cannot be used to copy the contents of an entire disk.
Discopy is not a built-in command in DOS. It is a program that can be installed on a DOS system.
Hard disks are not supported by the original version of Diskcopy. However, later versions of Diskcopy can be used to copy the contents of a floppy disk to a hard disk.