Understand the concept of domains in biology: Domains are the highest taxonomic rank in the classification of life. There are three domains: Bacteria, Archaea, and Eukarya.
Recall the characteristics of protists: Protists are a diverse group of organisms that are primarily unicellular, though some are multicellular. They have membrane-bound organelles, including a nucleus, which is a defining feature of eukaryotic cells.
Identify the domain that includes organisms with eukaryotic cells: The domain Eukarya encompasses all organisms with eukaryotic cells, including protists, plants, animals, and fungi.
Eliminate the incorrect options: Bacteria and Archaea are domains that consist of prokaryotic organisms, which lack a nucleus and membrane-bound organelles. Protista is not a domain but rather a kingdom within the domain Eukarya.
Conclude that protists are classified under the domain Eukarya based on their cellular structure and characteristics.