Which description best fits protozoa?

• A. Single-celled eukaryotes with animal-like nutrition and locomotion
• B. Plantlike, photosynthetic, multicellular organisms
• C. Parasitic worms
• D. Acellular infectious particles

Answer: (A)

Protozoa are single-celled eukaryotic organisms that move and feed in ways reminiscent of animals. Their nutrition is typically animal-like and heterotrophic, meaning they ingest or absorb organic matter rather than relying on photosynthesis. They exhibit locomotion through structures such as pseudopods, cilia, or flagella, which suits their mostly microscopic, aquatic or moist habitats. This combination—being single-celled, eukaryotic, and exhibiting animal-like feeding and movement—best fits protozoa. They are not plants (which are usually photosynthetic and may be multicellular), nor worms (multicellular and macroscopic), nor acellular infectious particles (viruses).