The correct answer is A. Carbon dioxide and water vapor.
The Earth’s first atmosphere was formed when the planet was still very young and hot. The gases that made up this atmosphere were released from the Earth’s interior by volcanoes and other geological activity. These gases were mostly carbon dioxide, water vapor, nitrogen, and hydrogen.
Over time, the Earth’s atmosphere changed as the planet cooled and the oceans formed. The water vapor in the atmosphere condensed and fell to the Earth’s surface, forming the oceans. This removed some of the water vapor from the atmosphere and caused the Earth’s temperature to drop further.
The Earth’s atmosphere also changed as life evolved on the planet. Plants began to photosynthesize, which removed carbon dioxide from the atmosphere and released oxygen. This change in the composition of the atmosphere allowed for the development of more complex life forms.
Today, the Earth’s atmosphere
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