Final answer:
The term 'gluten free' indicates a food contains no more than 20 ppm of gluten, helping to safeguard individuals with celiac disease.
Step-by-step explanation:
The FDA defines the term "gluten free" to mean that the food bearing the claim contains no more than 20 parts per million, or 20 mg or more gluten per kilogram (kg) of food. Therefore, the correct answer is D. 20, 20. This definition ensures the safety of individuals with celiac disease, a condition where consuming gluten leads to an immune response that damages the small intestine's villi. This damage can hinder nutrient absorption and lead to various health complications. Hence, foods labeled as gluten free offer a critical dietary option for maintaining health in affected individuals.