Which statement is true?

Which statement is true?

A.
An IPv6 address is 64 b long and is represented as hexadecimal characters.

B.
An IPv6 address is 32 b long and is represented as decimal digits.

C.
An IPv6 address is 128 b long and is represented as decimal digits.

D.
An IPv6 address is 128 b long and is represented as hexadecimal characters.