B. As a dietician, I must stress that we should eat fewer carbohydrates.
Explanation:
Ethos is a mode of persuasion that uses or mentions a source or figure that shows credibility, expertise, prestige or character in order to convince an audience that the information is reliable, valid, or worth listening. Sentence B is an example of ethos because it mentions an expert in human nutrition and the regulation of diet to convince people to eat fewer carbohydrates.
