The unstated assumption in this argument is "don´t eat meat" and if you do it "try to make it in small quantities".
Explanation: having a close look at the sentences, this is what is implicitly assumed-"eating large quantities of red meat is unhealthy" (do not consume meat, it can be harmfull for your health); in fact to be truly healthy, a vegetarian diet is preferable to one that includes meat. (if you really want to be healthy and follow a healthy diet, just concume veggies and get rid of meat).
Answer:
A 2013 preliminary study at UCLA on the effect of antioxidants found in pomegranates on memory.
Explanation:
The rest of the sources are either not credible in terms of research such as the magazine article and the trainer. The advertisement has bias when providing information making the study the best choice.
If I'm not mistaken your answer is C :)