The Creative Commons version of Public Domain licensing is:

The Creative Commons version of Public Domain licensing is represented by No Rights Reserved (CC0). The CC0 license allows creators to waive all their rights to their work worldwide under copyright law, including all related and neighboring rights, as far as the law allows. This puts the work as close to the public domain as possible, allowing anyone to use the work for any purpose without any restrictions.

Here’s a brief explanation of the other options, which are not equivalent to public domain:

• NoAttribution-ShareAlike (CC BY-SA): This does not exist as described. The closest is Attribution-ShareAlike (CC BY-SA), which requires attribution and that derivatives be shared under the same license but is not a public domain license.
• Attribution-NonCommercial (CC BY-NC): This license allows others to remix, tweak, and build upon the work non-commercially, and although their new works must also acknowledge the creator and be non-commercial, they don’t have to license their derivative works on the same terms.
• Attribution-NonCommercial-ShareAlike (CC BY-NC-SA): This license lets others remix, tweak, and build upon the work non-commercially, as long as they credit the creator and license their new creations under the identical terms.
• Attribution (CC BY): This license allows others to distribute, remix, adapt, and build upon the work, even commercially, as long as they credit the creator, providing a link to the license.

CC0 is the correct answer if you’re looking for the Creative Commons license that most closely aligns with placing a work in the public domain.