- Mon Aug 21, 2017 4:48 pm
Interesting point, nutcracker! Yes indeed, answer C does require assuming that every hemoglobin molecule is just about the same as every other hemoglobin molecule in both of those respects. If this was a pure Must Be True question, C would not be a very good answer at all.
However, this is a Most Strongly Supported question, the weak little brother to Must Be True, and in these questions we want to focus on what is most likely to be true, which one follow the stimulus the most and seems to be the most reasonable inference to draw, even if it isn't absolutely necessary. Is it reasonable to believe that hemoglobin molecules are all the same as each other in those two respects? Maybe. Given that they open up each time they pick up an oxygen molecule, and there has to some upper limit on how much they can open up, it seems reasonable to believe that any given one that has picked up three is probably more open than another that has picked up only one. Not certain, mind you, but reasonable. Maybe that's why they didn't compare one to two or two to three?
Is it reasonable to assume that once a hemoglobin molecule has picked up three oxygen molecules that it will pick up a fourth? Maybe, but that will also require at least one key assumption, and that's that there are more oxygen molecules around to pick up! What if there are none? Is it reasonable to assume that there are always more available to be picked up? I'm not sure about that.
You've raised a point that might be worth further debate with the authors of the test! You're not wrong, in my view, but I think you might be slightly over-thinking this one, and maybe allowing your dislike of one answer to lower your defenses to the flaws in another. Don't get too hung up on this one question, as I don't think you are likely to find many more where the answer is as open to debate as this one might be.
Finally, review this one again, and ask yourself, of the two answers under contention, why is A better than C? What makes you feel so sure about that probability in A? Picking the best answer is what this is all about, which means sometimes the credited response is lousy. That's okay, as long as it is better than the others. C needs less help here, in my opinion, and the assumptions you have to make seem more reasonable under the circumstances in than the ones required by A.
Keep up the good work and deep analysis! That will do you a lot of good on this test, usually.
Adam M. Tyson
PowerScore LSAT, GRE, ACT and SAT Instructor
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