Final answer:
The sentence 'Multiply by cell division. _____ are produced and passed in the feces, and they remain in the environment and infect other mammals.' should be completed as 'Protozoa / Infectious oocysts / Environmental stages' to accurately describe a category of parasites.
Step-by-step explanation:
The correct completion for the sentence describing a distinctive feature of the given category of parasites that multiply by cell division and produce stages that are passed in the feces is: Protozoa / Infectious oocysts / Environmental stages.
Protozoa are eukaryotic organisms that can be parasitic, carrying out their life cycle within a host or hosts. These include organisms like Giardia and Eimeria, some of which are pathogenic to humans and animals. Many protozoa transform into an infectious oocyst stage that is resistant and can survive in the environment for prolonged periods. These oocysts are shed in the host's feces and can infect other mammals when they come into contact with contaminated soil, water, or food. Thus, oocysts represent the environmental stages of their life cycle that play a crucial role in the transmission and survival of these parasites.