ans is (d)
a is not ans because A MAC address is given to a network adapter when it is manufactured. It is hardwired or hard-coded onto your computer's network interface card (NIC) and is unique to it. Something called the ARP (Address Resolution Protocol) translates anIP address into a MAC address.
A "media access control address" (MAC address) also called "Physical Address" is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and WiFi.
The original IEEE 802 MAC address comes from the original Xerox Ethernet addressing scheme. This 48-bit address space contains potentially 248 or 281,474,976,710,656 possible MAC addresses. All three numbering systems use the same format and differ only in the length of the identifier.