TOEFL Reading: ETS-TOEFL阅读机经 - OZW_0FL33Q3L1MCUL$

What can be inferred from paragraph 4 about "Earth's first stable atmosphere" A. It existed before Earth was yet fully formed. B. It contained very little hydrogen and helium. C. It contained only materials that had bubbled up through Earth's surface. D. It lacked water vapor.