An organism is unicellular, has a well-defined nucleus and may possess cilia or flagella. In which kingdom should it be
A unicellular organism with a well-defined nucleus is eukaryotic and therefore does not belong to Monera. Kingdom Protista includes single-celled eukaryotes, some of which possess cilia or flagella.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Kingdom Monera - Archaebacteria and Eubacteria