Which of the following, if true, would most weaken the author's conclusion about the hydrogen sulfide theory? A. The oceanic sediment is geologically inactive. B. Changes in the chemical composition of oceanic sediment have rendered the Permian period indistinguishable from earlier periods. C. The oceanic sediments of the Permian period contain unusually high levels of carbon. D. The oceanic sediments contain many chemicals more toxic than simple hydrogen sulfide. E. The oceanic sediments can mask large populations of other types of bacteria.