Final answer:
Jessica's sentence 'Vegan philosophy is the coolest philosophy today' should be rephrased to something more academic like 'Adopting a vegan philosophy is gaining prominence due to its potential health benefits and low environmental impact' for her argumentative essay.
Step-by-step explanation:
To make the language more appropriate for an argumentative essay on veganism for a nutrition class, the student should aim for an academic tone and objective language. Instead of saying "Vegan philosophy is the coolest philosophy today," a more suitable alternative could be: "Adopting a vegan philosophy is gaining prominence due to its potential health benefits and low environmental impact." This revision not only removes the subjective term "coolest," but also introduces the idea that the philosophy is notable for specific, evaluative reasons, which are supported by research and evidence in the realm of nutrition and environmental studies.