Final answer:
Options B (2001:db8::1) and D (ABCD:1234::5678) are valid IPv6 addresses. Options A and C are IPv4 addresses and thus are not correct choices.
Step-by-step explanation:
Among the listed options, the valid IPv6 addresses are:
- B) 2001:db8::1
- D) ABCD:1234::5678
Option A (256.128.40.10) and Option C (192.168.1.1) are not IPv6 addresses; they are in the format of IPv4 addresses. IPv4 addresses are typically composed of four octets separated by dots, with each octet ranging from 0 to 255, thus 256 in Option A is not a valid segment. IPv6 addresses, such as options B and D, are characterized by 8 groups of 4 hexadecimal digits, separated by colons, and can utilize zero compression (as in the :: notation).