The first atmosphere a. consisted mainly of water, carbon dioxide, carbon monoxide, and methane. b. was replaced by a secondary atmosphere that, arguably, consisted partially of gases brought to the Earth by comets. c. was replaced by a secondary atmosphere only after the Earth developed gravity, which helped deflect the solar wind. d. dissolved into the Earth's oceans before it was replaced by a second atmosphere.

Hence the correct option is option b - was replaced by a secondary atmosphere that, arguably, consisted partially of gases brought to the Earth by comets.

Explanation:

The first atmosphere was formed during the formation of the world.  

But the secondary atmosphere formed mainly 2. billion years ago by earth's internal volcanic activity, or by the buildup of fabric from comet impacts.

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