Final answer:
The invalid IPv6 address from the choices given is 2001:db8::7::2b, which contains multiple instances of '::', creating ambiguity.
Step-by-step explanation:
The address that does not represent a valid IPv6 address is 2001:db8::7::2b.
In IPv6, address format utilizes hexadecimal numbers separated by colons (:). A double colon (::) can be used once in an address to represent any number of consecutive sections of 16-bits of zeroes. If a double colon were to be used more than once, it would create ambiguity in the address as to the length of each block of zeroes being represented. This is why 2001:db8::7::2b is not valid since it contains two instances of double colons, making it impossible to determine the intended number of bits in each section.
Valid IPv6 addresses from the options given are ff02::1:0:0::a, 2001:3::7:0:2, 2000:0000:0000:0000:0000:0000:0000:0001 (which can also be shortened to 2000::1), and 2::1.