Which statement describes a facultative parasite?

A facultative parasite is defined as an organism that can live independently of a host but may also engage in parasitic behavior when the opportunity arises. This flexibility allows it to thrive in various environments, switching between a free-living lifestyle and a parasitic one, depending on the available resources and conditions.

In contrast to the other options, a facultative parasite does not rely exclusively on a host for survival, which is a defining characteristic of obligate parasites. The distinction lies in the adaptability of facultative parasites; they can survive without a host, whereas other types are dependent on their hosts for their life cycle or energy needs. This adaptability makes facultative parasites more versatile in their habitat and survival strategies.

The options that suggest exclusive dependence on a host or living in a specific characteristic related to the host's blood are descriptors for other types of parasitic organisms and do not fit the broader definition represented by facultative parasites.