Which kingdom would a newly discovered organism, multicellular and with eukaryotic cells but lacking photosynthesis, belong to?

The newly discovered organism is multicellular, has eukaryotic cells, and lacks the ability to perform photosynthesis. This description aligns with the characteristics of organisms in the Fungi kingdom. Fungi are primarily heterotrophic, meaning they obtain their nutrients by absorbing organic material from their environment, rather than producing their own food through photosynthesis like plants.

In addition, fungi have a unique structure that includes cell walls made of chitin, setting them apart from plants, which have cell walls made of cellulose. The fact that the organism is multicellular also supports its classification in the Fungi kingdom, as many fungi form complex structures such as mushrooms and molds.

The other kingdoms do not fit as well based on the provided characteristics. Plantae would involve photosynthetic organisms, while Animalia consists of multicellular, eukaryotic organisms that are heterotrophic but typically have more complex tissues and systems. Protista is a more diverse group that includes both unicellular and some primitive multicellular eukaryotes, often with varied methods of obtaining energy, but given the specific multicellular and eukaryotic context, Fungi is the most accurate classification.