Which of the following best describes a characteristic of parasites?

A defining characteristic of parasites is that they thrive on living hosts for sustenance. Parasites depend on their hosts for nutrients and, in many cases, to complete their life cycles. By living on or within their hosts, parasites can extract resources that are essential for their survival and reproduction, often to the detriment of the host's health.

This characteristic sets parasites apart from other organisms. For instance, organisms that might survive in extreme environments do not necessarily require a host for resources. Fungi that decompose organic matter play a vital role in ecosystems by recycling nutrients, but they do not require a living host. The idea that parasites are beneficial to human health does not apply, as their relationship with hosts typically involves detriment, such as disease or malnutrition.

Recognizing the relationship between parasites and their hosts is crucial in understanding their nature and impact on health and ecosystems.