Which definition correctly describes a parasite?

A parasite is defined as an organism that benefits from another organism, known as the host, at the expense of that host. This relationship is characterized by the parasite obtaining nutrients or resources from the host while potentially causing harm or detriment to the host's health or wellbeing. This behavior can manifest in various forms, such as feeding on the host's tissues, consuming its resources, or even causing diseases.

The nature of parasitism distinguishes it from other types of biological interactions. In mutualism, for example, both organisms benefit from the relationship, while in commensalism, one organism benefits without significantly affecting the other. The definition provided in the correct choice highlights this key aspect of parasitic relationships, emphasizing the unbalanced nature of the interaction where the parasite thrives at the host’s expense.