Which of the following is an example of a parasite?

Scabies is an example of a parasite because it is caused by a tiny mite, specifically Sarcoptes scabiei, which burrows into the skin and feeds on human blood. This condition is characterized by intense itching, inflammation, and is often spread through close personal contact. In the context of parasitism, scabies effectively illustrates how these organisms can live on or in a host organism, deriving their nutrients at the host's expense and often causing harm.

The other options represent different categories of organisms. Fleas and lice are also parasites, as they attach to the host and feed on its blood. Molds, on the other hand, are a type of fungus and do not classify as parasites because they do not typically derive nourishment from a live host but rather decompose organic material. Thus, while scabies exemplifies a parasitic relationship through its mode of living and feeding, the importance of understanding different types of parasitic organisms is crucial in fields like health and hygiene.