Which option is a valid IPv6 address?

A.
2001:0000:130F::099a::12a

B.
2002:7654:A1AD:61:81AF:CCC1

C.
FEC0:ABCD:WXYZ:0067::2A4

D.
2004:1:25A4:886F::1

Explanation:
http://www.ipv6.com/articles/general/IPv6-Addressing.htm
IPv6 Address Notation
IPv6 addresses are denoted by eight groups of hexadecimal quartets separated by colons in
between them.
Following is an example of a valid IPv6 address: 2001:cdba:0000:0000:0000:0000:3257:9652
Any four-digit group of zeroes within an IPv6 address may be reduced to a single zero or
altogether omitted.
Therefore, the following IPv6 addresses are similar and equally valid:
2001:cdba:0000:0000:0000:0000:3257:9652
2001:cdba:0:0:0:0:3257:9652
2001:cdba::3257:9652
The URL for the above address will be of the form:
http://[2001:cdba:0000:0000:0000:0000:3257:9652]/