The primary purpose of the passage is to A. present several hypotheses concerning the cause of the Permian mass extinctions B. discuss the strengths and weaknesses of the asteroid hypothesis of the Permian mass extinctions C. propose that theories regarding the cause of the Permian mass extinctions be tested D. argue that Permian mass extinctions could not have been caused by a volcanic explosion E. describe one reason that a rise in hydrogen sulfide would cause massive marine extinctions