A biologist conducting a study of how toxins move among multiple organisms and through water, soil, and air is working on a level of ecological study

The biologist is working on ecosystem level of ecological study.

Explanation:

The ecosystem of ecological study Is the study that comprises of the large communities of living organisms i.e plants, animals, microbes also called the biotic factors interacting or linked with the non living aspects of the environment known as abiotic factors. The known living aspects are water, soil, air e.t.c.

The biologists study is an ecosystem level of ecological system because He or she is studying toxin flow from biotic factors to abiotic factors.

option c is the correct answer.