Which type of parasites live in a host but release juvenile stages outside the host's body?

The correct choice is macroparasites. Macroparasites are larger parasites, such as helminths (worms) and arthropods, that typically live within a host and complete part of their life cycle outside the host. They often produce juvenile stages or eggs that are released into the environment where they can infect new hosts. This life cycle strategy allows them to maintain their population in the environment and ensures the continuation of their species through transmission to new hosts.

In contrast, microparasites are generally microscopic and include bacteria, viruses, and protozoa, which often reproduce inside the host without releasing juveniles outside. Endoparasites live primarily inside the host's body, relying on the host for their entire life cycle, without releasing juvenile forms into the external environment. Ectoparasites attach to the outside of the host, such as fleas and ticks, and do not typically release juvenile stages outside, as they directly feed on the host's bodily fluids.

Understanding these distinctions in parasite life cycles helps clarify their interactions with hosts and their ecological roles.