In the correct answer choice, a possible alternative explanation is eliminated. The other answer choices don't really do this, and don't really affect the argument at all. We can see this when we view their negations:
Negate (A): meteorite that strikes exactly the same spot won't obliterate all traces of earlier impact. Negate (B): The rates don't vary within any given region over time. Negate (C): Rate at which earth is struck hasn't greatly increased. Negate (E): More geologically stable regions haven't been studied more intensively.
And we can see that the argument still stands with these negations; thus, they can't be the answer choices we're looking for. Hope this helps!
rebutApril 2, 2020
You can negate sufficient strengthen answers? I thought that was only for necessary strengthen.
IbrahimApril 20, 2020
I have the same question that Nicholas had. How does negating the answer choices help us figure out which answer is correct when strengthening with sufficient premise?
shunheMay 3, 2020
Hi @Nicholas and @Ibrahim,
So the way I was thinking about it was that let's say you assume (A). Does it help properly draw the argument? Well, negate it and see if the argument can stand without it. But yes, there are other reasons that these answer choices are wrong:
Let's say (A) is true. But there's no reason to believe this would affect only the stable regions, so it wouldn't make a difference.
Let's say (B) is true. But it doesn't matter if the rates vary over time; we don't know enough about the actual variations.
Let's say (C) is true. Let's say the rate has increased. But there's no reason to believe this affects stable regions more than unstable ones.
Let's say (E) is true. This actually could weaken the argument, since it gives us another reason for finding more craters (scientists investigating those regions more).
