We group artworks with similar characteristics into periods or styles because it is easiest to do it that way - this way we can find common characteristics in these literary/artistic eras, and name them. For example, the Renaissance had a distinct style, which differs greatly from that of Romanticism.
I believe it is B but I’m not 100% sure
Im not 100% sure but the best answer I can give is Prokaryotes because they came to be around the time oxygen did as well.
