The MAC address is a 6-byte address expressed in six pairs of hexadecimal values. Because it is hexadecimal, only the letters A through F and numbers can be used. Answer B is incorrect because MAC addresses are expressed as six hexadecimal pairs. Answer C is an example of an IPv4 address. Answer D is an example of an IPv6 address. Answer E is incorrect because MAC addresses are expressed in hexadecimal; therefore, only the letters A through F and numbers can be used.