IPV$4$ is

$($a$)$ bits long providing over $4$ billion addresses, which have now been exhausted. IPv$6$ is its replacement and uses

b$)$ bits, doubling the number of addresses for every additional bit used.

$($a$)32,($b$)128$

$($a$)64,($b$)128$

$($a$)16,($b$)32$