Final answer:
Due to biological magnification, the highest concentration of a chemical herbicide would be found in the hawk.
Step-by-step explanation:
Biological magnification is the increasing concentration of persistent, toxic substances in organisms at each trophic level. The highest concentration of a chemical herbicide due to biological magnification would be found in the hawk, which is a predator of mice. This is because the herbicide would accumulate and become more concentrated as it moves up the food chain from the primary producer (grass) to the herbivore (cow) to the predator of mice (hawk).