Answer:
it is an adventure phrase that modifies the adjective letter
Superlative means exaggerated.
Comparative means it is being compared to something else.
Positive is self-explanatory.
Honestly this is a hard one because usually when someone says something is "the best" they are exaggerating. Also when you say something is the best, youare saying that the other things you have tasted aren't as good which compares the omelet. Since your not saying the omelet is bad it is a good (positive) comparison. I think the closest answer is comparative for the reasons above.
Ethos: appeal to credibility
For example someone including a specialist or professional's opinion on a product.
Ex: #1 Doctor Recommended
Ex: Selena Gomez's Favorite Shampoo
