Hey there!
A MAC, or Media Access Control, Address is a unique identifier that is assigned to devices connected to a network. It is 6-bytes, or 48-bits, in size. It follows the format MM:MM:MM:SS:SS:SS, where the first 3-bytes are the identification number of the manufacturer and the second 3-bytes are the serial number assigned by the manufacturer.
Your answer will be D.
Hope this helped you out! :-)