Valid IPv6 Address

C

Out of the given options, only option C is a valid IPv6 address. Let's understand why:

IPv6 addresses are 128-bit addresses written in hexadecimal notation. Each 16-bit block is separated by a colon. In addition, IPv6 uses the double colon (::) to represent consecutive 16-bit blocks of zeros. However, this can only be used once in an address.

Now let's examine each of the given options to see if they are valid IPv6 addresses:

A. FECO:3313:9734 :W067::2A4

This option is not a valid IPv6 address because it contains an invalid character 'W'. IPv6 addresses only use hexadecimal characters (0-9, A-F).

B. 2001:0000.130F::099a::12a

This option is not a valid IPv6 address because it contains a dot '.' instead of a colon ':' in the middle. IPv6 addresses do not use dots.

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

This option is not a valid IPv6 address because it contains too many blocks. IPv6 addresses have only 8 blocks of 16-bit each. This option has 9 blocks.

Therefore, the correct answer is C. 2004:1:25A4:886F::1. This address has 6 blocks, with the double colon used to represent consecutive blocks of zeros.