Which of the following kingdoms has/have only unicellular organisms?

In the five-kingdom classification system, Kingdom Monera consists exclusively of unicellular prokaryotic organisms, such as bacteria and cyanobacteria. Kingdom Protista is defined as containing all unicellular eukaryotic organisms, including protozoans like Amoeba and unicellular algae [4]. While some sources mention that certain protists can be colonial or simple multicellular, the standard biological definition for competitive exams identifies Protista as the kingdom for unicellular eukaryotes [3]. In contrast, Kingdom Fungi includes both unicellular members like yeast and multicellular members like bread mould. Similarly, the kingdoms Plantae and Animalia are primarily multicellular [1]. Therefore, both Monera and Protista are the primary kingdoms characterized by unicellularity, distinguishing them from the predominantly multicellular eukaryotic kingdoms.

Sources

1. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.5 Why Is Cell Considered to Be a Basic Unit of Life? > p. 23
2. [4] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > 2.3 What Are Microorganisms? > p. 15
3. [1] https://nios.ac.in/media/documents/srsec314newe/lesson-02.pdf