Which of the following best defines Monera?

Monera refers to a kingdom that encompasses all prokaryotic organisms, which are characterized by their lack of a defined nucleus and other membrane-bound organelles. The defining feature of Monera is that its members are unicellular, meaning they consist of a single cell. This kingdom includes bacteria and archaea, which thrive in various environments, from soil to extreme conditions. The classification of Monera distinguishes it from other kingdoms, such as those containing multicellular organisms like fungi, plants, and animals, which are eukaryotic and have complex cellular structures. Thus, the option that describes Monera as unicellular prokaryotic organisms is accurate and captures the essence of this biological classification.