A protozoan having a flagellum would be classified in which genus?

The classification of a protozoan that possesses a flagellum is linked to its movement and life cycle characteristics. Trypanosoma is a genus of flagellated protozoans that are known for their distinctive whip-like flagella, which they use for motility. These organisms are often associated with diseases, such as African sleeping sickness, and are typically found in various environments, depending on the specific species.

In contrast, the other genera listed do not include flagellated protozoans. Plasmodium is known for its role in malaria and does not have flagella; it primarily exists in the bloodstream in an intracellular form. Amoeba and Entamoeba are both characterized by their ability to move via pseudopodia, a form of movement that involves the extension of their cell body rather than flagella. Therefore, the presence of a flagellum specifically identifies Trypanosoma as the correct choice in this context.