Which one of the following is not an example of eukaryotic organism?

Living organisms are classified into two broad categories based on cell structure: prokaryotes and eukaryotes. Eukaryotic organisms possess complex cells with a membrane-bound nucleus and specialized organelles. This group includes animals (such as human beings), plants, fungi (such as yeast), and protists [1]. In contrast, prokaryotic organisms lack a defined nucleus and membrane-bound organelles, with their genetic material residing in a nucleoid region. Bacteria and Archaea are the primary examples of prokaryotes. While yeast is a unicellular organism, it is a fungus and thus eukaryotic. Human beings and plants are multicellular eukaryotes. Therefore, bacteria are the only organisms listed that are not eukaryotic, as they are fundamentally prokaryotic in nature.

Sources

1. [1] https://www.nature.com/scitable/topicpage/beyond-prokaryotes-and-eukaryotes-planctomycetes-and-cell-14158971/