Which kingdom consists of single-celled organisms with a true membrane-bound nucleus?

The kingdom that consists of single-celled organisms with a true membrane-bound nucleus is Protista. Members of this kingdom are characterized by having eukaryotic cells, which means they possess a defined nucleus and organelles that are enclosed by membranes. This differentiates them from organisms in the Monera kingdom, which are prokaryotic and lack a true nucleus.

Protista includes a diverse array of organisms, such as algae, protozoa, and some slime molds. Many of these organisms are unicellular, although there are also multicellular forms. The presence of a true membrane-bound nucleus is a defining feature of eukaryotic cells, making Protista the appropriate kingdom for single-celled organisms with this characteristic. Understanding the different classifications and organizational structures among living organisms is crucial for studying biology and life sciences.