What is a MAC address and at which OSI layer does it operate?

• A.MAC addresses are assigned by DHCP; address resolution requests are unicast to the default gateway, which answers on behalf of every host in the subnet, and the reply is then cached permanently because the protocol defines no expiry mechanism for the entries it has learned from the wire
• B.A MAC address is a software-assigned IP alias; network address translation is performed at layer 2 by rewriting the frame header, which is why a translating device has to sit in the same broadcast domain as every host it serves, and why the technique cannot be used when internal hosts are spread across several subnets
• C.MAC addresses work at Layer 7
• D.A MAC address (Media Access Control) is a 48-bit hardware identifier assigned to network interface cards, operating at Layer 2 (Data Link) - it's written as six pairs of hexadecimal digits (e.g., AA:BB:CC:DD:EE:FF) and is used for local network communication