Fungi are saprophytic or parasitic, so they are not autotrophic, but heterotrophic, and there is no chloroplast in the structure of that cell;

Algae belong to plants and live in water, which is the lowest plant group, but in the most basic structure of all plants, the outermost layer has cell walls, which play a supporting and protecting role. In addition, plants need photosynthesis, so there will be chlorophyll or chloroplast in cells, thus synthesizing organic matter independently;

Protozoa are unicellular animals, belonging to the phylum Protozoa in the animal kingdom. No matter whether the basic structure of animal cells is low or high, there will be no cell wall. And animals don't need photosynthesis, and of course cells don't contain chloroplasts.

So these three creatures can be simply distinguished in structure.