R. c. lewontin found that human "races" have no taxonomic significance. how did he demonstrate this?

Through research indicating that most genetic variation is found across human population

Im pretty sure it’s is c

Texas’ gulf coastal plains are the western extension of the coastal plain extending from the atlantic ocean to beyond the rio grande. its characteristic rolling to hilly surface covered with a heavy growth of pine and hardwoods extends into east texas. in the increasingly arid west, however, its forests become secondary in nature, consisting largely of post oaks and, farther west, prairies and brushlands.