The stim maps like this

DHB = develops health bones

DIC = Diet in calcium

If DHB → DIC

/DHB → /DIC

This is a mistaken reversal as the actual contrapositive of the premise is

/DIC → /DHB

Thus the stim has flawed conditional reasoning!!

AC A takes the contrastive properly — it is a sound argument

AC B performs the same mistaken reversal as the stim and is thus the correct answer

Your answer was incorrect because you accurately mapped the contrastive of the premise — the LSAt author did not!!

Not sure if this will help anybody, but I managed to get the correct answer the first time thinking about it like this:

AC A suggests that 'A factor (slipped discs in this case), does not need to be present for a certain affect (back pain), but may nonetheless be sufficient to bring about (back pain) in certain circumstances.

This is incorrect -- the stimulus experiment proves that a slipped disc is not sufficient to bring about back pain by demonstrating that some people have slipped discs without feeling any back pain!

AC B suggests that 'A factor (slipped disc) that is not itself sufficient to bring about an effect (back pain), may nonetheless contribute to back pain in certain circumstances.

This accurately describes questions structure and properly addresses the gap in reasoning and is thus the right answer!

I think placing an emphasis on finding the gap is detrimental for most necessary assumption questions. Many NA questions do not have gaps! Remember a necessary condition is just something that is required by the argument, not a condition that is sufficient for the argument; that will bring about the conclusion.

I think the previous lesson (a few back now) that showed the range of support was quite useful in this respect. Necessary assumption answers do not complete arguments, but rather save them from failing. If we don't assume D is true in this questions case, keeping things consistent with construction paper really doesn't matter, so the conclusion fails.

Not all necessary assumption questions will have a gap (in fact many will not)! I think the previous lesson that showed the range of support was quite useful in this respect. Necessary assumption answers do not complete arguments, but rather save them from failing.

The correct answer choice is necessary for the conclusion to occur, but the vast majority of the time it will not cause the conclusion to occur. So there doesn't have to be a gap to fill!

I'll do my best! The logical indicator 'without' is a group 3 negate sufficient -- which means we can take either of the two components make it the sufficient condition in our lawgic chart, and then negate that component. I'd re-watch the earlier videos on this if you're still confused as to why.

https://7sage.com/lesson/group-3-negate-sufficient/

'No A' already makes A a negative (before we can choose to negate it as per the group 3 'rule). If we choose this term to be the sufficient condition it will become a double negative, and thus we can cancel it to become a positive.

/ / A --> B

becomes simply A --> B

or sometimes I find it easier to mentally understand 'without' statements as the contrapositive

/B --> /A

I'll take a shot at it! I think finding the gap and bridging it makes the most sense here (you can likely save a whole bunch of diagraming just with a bit of intuition)

Just because a customer doesn't bother to do a cost-benefit analysis does meet the sufficiency of the premise; they have to expect that it will not be worth it, which still requires some thought, not doing nothing (bothering to think) at all.

E is the only answer choice that fills these gaps. I think most of the other answer choices in this case can be eliminated quite quickly (or at least arm bells should be going off) because of the word 'usually.' The conclusion is exact, and says nothing about what usually happens.

LMK if you need anymore clarification -- it helps a lot to think about why!

You can think of it as /I, so long as you write the argument in the contrapositive to what the video demonstrated

honestly very confusing wording.

Re-written: If you did not RSVP then you are not invited.

IF /RSVP --> /I

R/RSVP

Therefore Rudy is not invited.

Just because there is a relationship between two statements doesn't mean there is an argument. I think you could take a classic argument to see this more simply.

Socrates is a man

all men are mortal.

If there is no conclusion it's not an argument. There is no persuasion. I think you could easily infer a conclusion or make an argument from the information in the statements of this question, but it just ends abruptly and does not try to persuade the reader.