GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - 3E3O935Q4K5UZ3YTJ

Which of the following can be inferred from the passage about methanogens? A. Methanogens must have appeared on Earth later than 2.3 billion years ago. B. Methanogens must have been much more prevalent in some regions of the early Earth than in others. C. Methanogens produce a greenhouse gas that is more susceptible to destruction by the Sun's ultraviolent rays than is ammonia. D. Methanogens could not have thrived in early Earth's atmosphere without the presence of ammonia. E. Methanogens would have had a less significant effect on early Earth's atmosphere if they had evolved after the appearance of cyanobacteria.