Currently, the biological world is recognizing six kingdoms that are presently residing on earth. They are the kingdoms Animalia, Fungi, Plantae, Protista, Archaea and Bacteria. We can answer the question based on classifying each characteristic given to the characteristic of each kingdom.
Single celled -> Animalia and Plantae are not single celled organisms. Fungi and Protista both have single celled and multi cellular organisms. So we are down to Kingdoms Fungi, Protist, Archaea and Bacteria.
Photosynthetic -> Fungi are not photosynthetic. Plants are photosynthetic however they are disregarded since they are not single celled organisms. The remaining kingdoms are the Protista, Archaea and Bacteria.
Nucleated -> Organisms that are nucleated means that it has a nucleus bound in a nuclear envelope. Only Archaea and Bacteria are non-nucleated. From the remaining choices, Kingdom Protista is the only nucleated organism.
Final answer: Kingdom Protista (protists)
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