Which of these sentences from jack london's "the human drift" is an example of naturalist writing?

a. there have been drifts from east to west and west to east, from north to south and back again, drifts that have criss-crossed one another, and drifts colliding and recoiling and caroming off in new directions.
b. man early discovered death. as soon as his evolution permitted, he made himself better devices for killing than the old natural ones of fang and claw.
c. in the misty younger world we catch glimpses of phantom races, rising, slaying, finding food, building rude civilisations, decaying, falling under the swords of stronger hands, and passing utterly away.
d. perhaps most amazing has been the south sea drift. blind, fortuitous, precarious as no other drift has been, nevertheless the islands in that waste of ocean have received drift after drift of the races.