Final answer:
Digestion involves chemical change because new substances are produced.
Step-by-step explanation:
The best evidence that digestion involves chemical change is D. New substances are produced. In chemical reactions, the components of the reactants are all present in the products, and there is nothing present in the products that is not present in the reactants. This is because chemical reactions are governed by the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction.