Which command is used to concatenate all files beginning with the string 'emp' and followed by a non-numeric characters?

In Unix, the command cat emp[!0-9] is used to concatenate all files beginning with the string 'emp' and followed by a non-numeric character. Here, the square brackets denote character classes, and the exclamation mark (!) negates the character class. So, [!0-9] matches any character that is not a numeric character.
Therefore, Option A: cat emp[!0-9] is the correct command to concatenate all files beginning with the string 'emp' and followed by a non-numeric character.