Which of the following statements is true in regard to diskcopy?

In MS-DOS, diskcopy is a command used to duplicate the entire contents of one floppy disk to another. Here's an analysis of each statement:

Copy and diskcopy are the same:
This statement is false. While both copy and diskcopy are commands in MS-DOS, they serve different purposes. Copy is used to copy files, whereas diskcopy is used to duplicate entire disks.

Discopy is a built-in command in DOS:
This statement is false. There is no discopy command in MS-DOS. The correct command for disk duplication is diskcopy.

Diskcopy can be used on hard disks:
This statement is true. Although diskcopy is primarily used for floppy disks, it can also be used to copy data between floppy disks and hard disks.

Therefore, the correct answer is Option D: Diskcopy can be used with a floppy and a hard disk.