What are protozoa?

Protozoa are classified as one-celled animals, which makes the selection of this answer accurate. These microscopic organisms are primarily characterized by their single-celled structure and complexity, functioning independently and exhibiting characteristics typical of animal behavior, such as movement and predation. Protozoa can inhabit various environments, including water, soil, and even within other organisms.

The other options do not accurately describe protozoa. Multi-celled organisms refer to organisms made up of many cells, such as plants and animals, which is different from the single-celled nature of protozoa. Plants that grow in water are classified as aquatic plants and do not share the characteristics of protozoa, as they are multicellular and photosynthetic. Lastly, fungi that decay organic matter are a separate kingdom of life entirely and do not align with the definition of protozoa, which belong to the kingdom Protista. Understanding these distinctions helps clarify the biological categorization of different types of organisms.