Answer:
Letter C is the correct option.
Step-by-step explanation:
A fluff, understood as a mistake or as something not accurate, is reflected in option C. All the other options provide evidence in one way or another: A and B mention specific data, numbers -50% of current American diet- or chemical substances such as Butylated hydroxytoluene. Option D is also a statement that resumes the given information and its clear and convincing. On the other hand, C states something that looks more like and opinion or speculation. It is even contrasting with other excerpts from the text (the high percentage of people that consume this kind of food), making it a fluff.