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Atmosphere

APBIO-OM4K5W

Hypotheses about the composition of Earth's atmosphere prior to the development of life have changed over the years. However, scientists have consistently agreed that some molecules were not present in the atmosphere when the first biological molecules formed.

Which of the following is a gas that scientists hypothesize became part of the atmosphere after the first life formed?

A

Carbon dioxide.

B

Methane.

C

Nitrogen.

D

Oxygen.