TOEFL Reading: ETS-TOEFL阅读机经 - 3MV1T5L6O2X4ZX_1L$

Paragraph 2 supports which of the following statements about methane and carbon dioxide present in Earth's earliest atmosphere? A. They slowed down the loss of heat from Earth's atmosphere. B. They caused the sunlight to be less bright than it currently is. C. They occurred in smaller amounts than they currently do. D. They prevented the development of early life-forms.