This a strengthen question. The author argues that nutrition experts would have more success in encouraging people to eat healthy if they focused on flavor versus nutrition because flavor is the primary concern for most people.
Let's look at (D).
(D) is wrong because the author argues that the likelihood of success in encouraging someone to eat depends on one's perception of this particular food rather than comparative perception among foods. Let's say a nutritionist is trying to convince someone to try acai, their best approach would be is to focus on its flavor rather than nutritional benefits according to the argument. It is irrelevant whether acai is more flavorful than quinoa. (D) suggests that when choosing among foods, it turns out that most flavorful ones are least nutritious, but this fact is irrelevant to our conclusion.