What term is used for unicellular and motile eukaryotes?

The term used for unicellular and motile eukaryotes is "protists." Protists are a diverse group of organisms that can exhibit various forms of locomotion, including flagella and cilia. They are primarily classified as eukaryotic organisms that can be unicellular or multicellular, but many of them, such as certain types of algae and protozoa, are unicellular and can be found moving through their aquatic environments. The motility seen in many protists allows them to interact with their surroundings and search for food or mates.

Yeast, while unicellular, is a type of fungus and typically does not exhibit motility. Bacteria are prokaryotic organisms, which lack a nucleus and other membrane-bound organelles, making them fundamentally different from eukaryotic protists. Molds, similar to yeast, are fungi and are usually filamentous, not predominantly unicellular and motile. Thus, the unique characteristics of protists make them the correct answer in this context.