Answer :
An essay about the differences between tomatoes and corn is most likely to be a compare and contrast essay. This type of essay is used to study the similarities and/or differences between two separate subjects (here tomatoes and corn). This type of an essay not only points out the similarities or differences between the subjects but also uses the mentioned points to make a relevant argument about these subjects.
D. The main ideas listed in the question are arranged according to the order of comparison and contrast.