Rank the order of these diets, from highest climate impact to lowest: beef-free, vegan, average, beef-intensive, vegetarian.
a. beef-intensive, beef-free, average, vegetarian, vegan
b. beef-intensive, beef-free, average, vegan, vegetarian
c. average, beef-intensive, vegetarian, beef-free, vegan
d. beef-intensive, average, beef-free, vegetarian, vegan