How does GMAC improve on the HMAC process?

GMAC produces $128-$bit hashes as opposed the $256-$bit hashes produced by an HMAC. This makes GMAC more secure$.$

The GMAC process does not require a secret key, while the HMAC process uses a secret key. This makes GMAC more secure as there's no need for the sender and recipient to exchange koys.

In addition to providing authentication, the GMAC process provides error correction capability. It can be used to detect and repair bits that were changed during transmission.

The GMAC process hashes the message twice, making it impervious to Length Extension Attacks. The HMAC process only performs a single hash, leaving it vulnerable to Length Extension Attacks.

The GMAC process provides the ability to authenticate more than just the encrypted message. With GMAC, and desired additional data can also be authenticated.

None of the above