External command in DOS are

Answer: Option A

External commands in Disk Operating System (DOS) are commands that are implemented as separate executable files (.exe or .com) stored in a directory specified in the PATH environment variable. They are not built into the command interpreter (command.com).

Among the options provided:
Option A, "Copy, edit, sys, format," includes commands that are external commands in DOS.
Option B, "Edit, sys, chkdsk," includes some external commands but not all listed are external commands.
Option C, "Chkdsk, prompt, date," includes some commands that are typically internal commands.
Option D, "Sys, ver, vol," includes some commands that are typically internal commands.

Therefore, the correct answer is Option A: Copy, edit, sys, format.