What kingdom includes organisms such as algae and protozoans?

The kingdom that includes organisms such as algae and protozoans is Protista. This kingdom is characterized by its diverse group of eukaryotic microorganisms. Protists can be unicellular or multicellular and display a wide range of forms and functions. Algae, which can be found in various aquatic environments, are photosynthetic and contribute significantly to ecosystems as primary producers. Protozoans are primarily heterotrophic and often play essential roles in nutrient cycling within their environments.

In contrast, the other kingdoms listed consist of different types of organisms: Fungi are primarily decomposers that absorb nutrients from organic matter, Eubacteria comprises prokaryotic microorganisms that can be found in various environments, and Animalia consists of multicellular organisms that are primarily heterotrophic. Thus, Protista is the correct choice as it specifically encompasses the diversity presented by algae and protozoans.