Answer:
The correct answer is option C. "Hermann von Helmholtz’s demonstrations that energy is converted but not created when animal muscles move".
Step-by-step explanation:
Hermann Ludwig Ferdinand von Helmholtz was a notorious scientist that contribute to different fields, but was devoted to medicine and physics. He applied his knowledge in both fields to demonstrate that energy is converted but not created when animal muscles move. By doing so, he made an observation of a biological system (in this case the animal muscles) that contributed to the theory of conservation of energy.