Which of the following is classified as a non-parasitic organism?

Fungus is classified as a non-parasitic organism because it typically feeds on decaying organic matter or uses other types of metabolic processes rather than relying on a host for survival and reproduction. Unlike parasitic organisms that require a host to thrive and often cause harm to the host's body, fungi play different roles in ecosystems, including decomposers, and can also exist in symbiotic relationships without causing harm.

In this context, Rickettsial refers to a type of bacteria that are obligate intracellular parasites, meaning they must live within a host's cells to survive. Protozoans can be either free-living or parasitic, where certain species do depend on hosts for life cycles. Coccidia are a specific type of protozoan that are known to be parasitic, often infecting the intestines of their hosts. Thus, these organisms cannot be classified as non-parasitic.