As of January 1st, 2019, what changed regarding protected content?

The correct response highlights that, as of January 1st, 2019, certain revisions to copyright law caused a modification in the status of previously protected works. This indicates that while many items that were once protected continued to enjoy some level of copyright, certain specific categories or types of content underwent changes in their protectability, thus leading to the end of protection for some existing works.

Understanding this context is crucial, as it relates to ongoing discussions in copyright law about the duration and scope of protections. A shift could occur due to legislative changes aimed at addressing modern technology or creative industries, which are continually evolving.

The other options do not accurately reflect the nuances of copyright law post-2019. For instance, the revocation of all prior protections is too sweeping a statement and does not account for the continuity of some protections. The notion that previously protected items are wholly unprotected misrepresents the framework of copyright, while the idea that new works gained protection without registration does not address the complexities involved in copyright registration processes which still require consideration. Likewise, while certain revisions may not retroactively affect protections, this too does not capture the specific changes that occurred, especially for particular categories of works under the amended regulations.