Qn no 136 of advanced CR guide of current GMAT qns

I am stuck between choice d and e.  How choice d is breaking the argument and why e is incorrect I couldn’t figure out.

Beginner Asked on November 15, 2016 in Critical Reasoning.
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1 Answer(s)

The argument basically states that –

no two bacterial strains on Earth are different enough –> All bacteria currently on earth originated on Earth

Negate E –

There were some strains of bacteria that originated on Earth and died out. Does not weaken the conclusion –

All bacteria currently on earth originated on Earth

Negate D –

All bacteria on Earth currently originated on Mars. (Weakens the argument).

Expert Answered on November 15, 2016.
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