S₁: The earth was initially very hot and without an atmosphere.

S₆: This early atmosphere was not one in which we could have survived.

P: The atmosphere came from the emission of gases from the rocks.

Q: Because it contained no oxygen.

R: In the course of time it cooled and acquired an atmosphere.

S: But it contained a lot of other gases that are poisonous to us.

The proper sequence should be

English 2013 CDS English 2013 CDS 2013

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