Final answer:
Protozoa are unicellular, heterotrophic, and motile organisms classified as protists, commonly known as microscopic animals, although not true animals. They use flagella, cilia, or pseudopods to move and can be part of many food webs.
Step-by-step explanation:
Protozoa (singular: protozoan) are a type of unicellular organism classified as protists. They are often referred to using the informal term protozoans, especially when discussing those that are nonphotosynthetic, motile, and single-celled. Protozoa exhibit a variety of motion mechanisms, such as flagella, cilia, or extensions of their cell body known as pseudopods. While most protozoa are harmless and form a fundamental part of many food webs, some can cause diseases in humans and other animals. In the context of the question provided, protozoa are best described as microscopic animals in the sense that they are animal-like because they are heterotrophic and capable of movement, although they are not actually animals. Therefore, the correct answer to the student's question is that protozoa are b) Microscopic animals.