gmataspirant9 wrote:Hi Ron;
Sorry for reopening this thread.
For options E, can't we infer that "because the earth's bacteria has died down and so Mars's bacteria is the only one which is surviving"
by writing the words that i put in boldface here, you have actually written a flawless justification of the correct answer choice (d).
choice (e) doesn't accomplish this reasoning, because it just says that some
earth-based bacterial forms have died out. there's no reason to take the statement to such an extreme -- especially when choice (d) is already an exact statement of that precise extreme.
E is wrong because we need to weaken the argument that the bacteria from mars has died out.
Pointing that bacteria from earth has died out will be out of scope as we still does not know that single strain of bacteria is from earth.
We just know that there are single strains of bacteria and concluding that they are not from mars.
So saying that all bacteria are from mars will most weaken the argument. Hence answer is D
Saying that bacteria from earth has died out will not negate the conclusion.