# Hemoglobin, a substance in human blood, transports oxygen from the lungs to the rest of the body. With each oxygen mo...

Golnar-Roughani on March 31, 2020

why C over A?

Can you please explain what makes C a better answer than A? I chose A but then after I realized that's wrong, I told myself the word 'probably' makes answer choice A wrong. Yet again, I thought to be myself, if answer choice had said: "a hemoglobin molecule always reaches its capacity of 4 oxygen molecules," would this make it the correct answer? I guess my problem is that I can't deduce from the passage that a hemoglobin molecule will always reach its capacity of 4 Oxygen molecules which is why picked A because it said "probably''. Can you please tell me where my thought process is wrong? Thanks!

Replies

shunhe on April 2, 2020

Hi @Golnar-Roughani,

Thanks for the question! First things first, recall that on the LSAT we need to find the best answer out of all the answer choices, not just adequate answers. (A) is certainly a possible answer based on what the passage tells us. But it makes a few key assumptions: for example, that there will be a fourth oxygen molecule around for a hemoglobin molecule that’s picked up three oxygen molecules to pick up. It could also be the case that the chance of hemoglobin molecules picking up oxygen in general is very low: maybe it’s still only 20% for a hemoglobin molecule with three oxygen molecules, and before then, it’s even lower—10%, 15%, 18%, then 20% for the last one. But then it’s not the case that the hemoglobin will probably acquire a fourth oxygen molecule, because the chance is much less than 50%.

(C), on the other hand, is more directly supported by the passage. Why? Because we’re told that with each oxygen molecule that hemoglobin picks up, it becomes more effective at picking up additional oxygen molecules. Thus, it would make sense that a hemoglobin molecule with three molecules would be more effective at picking up another oxygen molecule than will a hemoglobin molecule that’s only picked up one oxygen molecule. Now, it’s technically true that this assumes to some degree that we can consider all hemoglobin molecules equal if they’re at the same stage. But this is a much smaller assumption than the one we have to make for answer choice (A), which means that (C) is better than (A) for this most strongly supported question. Thus, we pick (C).

Hope this helps! Feel free to ask any further questions that you might have.

Dalaal on April 6, 2020

Could someone please repost the instructor's answer? It is not showing up for me.

shunhe on April 6, 2020

@Dalaal, hopefully it works this time. I think it might have to do with being on the most updated version of the app. Reposting what I wrote verbatim:

Thanks for the question! First things first, recall that on the LSAT we need to find the best answer out of all the answer choices, not just adequate answers. (A) is certainly a possible answer based on what the passage tells us. But it makes a few key assumptions: for example, that there will be a fourth oxygen molecule around for a hemoglobin molecule that’s picked up three oxygen molecules to pick up. It could also be the case that the chance of hemoglobin molecules picking up oxygen in general is very low: maybe it’s still only 20% for a hemoglobin molecule with three oxygen molecules, and before then, it’s even lower—10%, 15%, 18%, then 20% for the last one. But then it’s not the case that the hemoglobin will probably acquire a fourth oxygen molecule, because the chance is much less than 50%.

(C), on the other hand, is more directly supported by the passage. Why? Because we’re told that with each oxygen molecule that hemoglobin picks up, it becomes more effective at picking up additional oxygen molecules. Thus, it would make sense that a hemoglobin molecule with three molecules would be more effective at picking up another oxygen molecule than will a hemoglobin molecule that’s only picked up one oxygen molecule. Now, it’s technically true that this assumes to some degree that we can consider all hemoglobin molecules equal if they’re at the same stage. But this is a much smaller assumption than the one we have to make for answer choice (A), which means that (C) is better than (A) for this most strongly supported question. Thus, we pick (C).

Hope this helps! Feel free to ask any further questions that you might have.

alliehall21 on June 7, 2020

The explanation of why C over A still is not showing up