Which microorganism type feeds off humans or animals and typically lives in water?

The correct choice is the type known as parasites, which are organisms that live on or in a host and obtain nutrients at the expense of that host. Parasites can be found in various environments, including water sources. They often require a living organism (such as humans or animals) to survive and propagate. Examples of waterborne parasites include certain types of protozoa and helminths, which thrive in aquatic environments and can transfer to hosts through contaminated water.

In contrast, viruses are much smaller infectious agents that cannot reproduce outside a host cell and do not primarily feed off other organisms in the same way that parasites do. Bacteria, while capable of living in water, do not specifically feed off hosts; they can be either harmful or beneficial and can derive nutrients from their surrounding environment. Fungi are organisms that play a different role in ecosystems; they decompose organic matter and do not typically live in water as parasites, and they also do not have the same host-dependent feeding characteristic as parasites.

Understanding the unique characteristics of these microorganisms helps clarify why parasites are identified as the correct response to this question.