Q18

[c.s.sun5]

I put (C) for this instead of (E) and I could kind of see why (E) is the correct answer in that it's trying to say basically that there are some cells that die because they don't connect with the necessary cells to survive.

Is (C) wrong because the passage doesn't really speak of the cells which are needed in development?

[ManhattanPrepLSAT2]

(C) is a tempting answer, but (E) is more provable, and I think you are definitely on the right track as to why --

We're told that many more cells are created than end up connecting to their target tissues.

Therefore, it's logical to conclude that some of these cells do not connect to their target, which is what (E) states.

(C) goes too far beyond what (E) states and what the text states -- (C) says "few" of these cells are actually needed (the few, in this case, meaning very little) -- this is not provable based on the text -- it could be that many cells are needed (even if many are, as we're told in the text, not needed). Again, knowing that many are not needed DOES NOT allows us to infer that few are needed. As you stated, we don't know about how many are needed.

Hope that helps!

[zainrizvi]

(C) is a tempting answer, but (E) is more provable, and I think you are definitely on the right track as to why --

We're told that many more cells are created than end up connecting to their target tissues.

Therefore, it's logical to conclude that some of these cells do not connect to their target, which is what (E) states.

(C) goes too far beyond what (E) states and what the text states -- (C) says "few" of these cells are actually needed (the few, in this case, meaning very little) -- this is not provable based on the text -- it could be that many cells are needed (even if many are, as we're told in the text, not needed). Again, knowing that many are not needed DOES NOT allows us to infer that few are needed. As you stated, we don't know about how many are needed.

Hope that helps!

Can you please cite the exact lines where this is done? I'm getting a bit confused by the language of the passage.

[jimmy902o]

also, why is B wrong? i felt like that was a pretty sure thing...

[nflamel69]

the qualitative difference was never brought up in the passage

[ohthatpatrick]

Just to tidy up a few questions:

lines 16-20 are how we're supporting (E).

And as the previous poster, suggested, we have no information in the passage to justify the extreme claim that nerve cells in the absence of NGF are qualitatively identical to nerve cells that grow in the presence of NGF.

When the question stem uses wording such as:
what does the passage suggest
what does the passage imply
the passage most strongly supports
what can be inferred from the passage

you have to find a line reference to justify your answer, and you should be very dubious of any answer that has extreme wording (unless you can justify that extreme word with a line reference).

Hope this helps.

[Nina]

is A wrong because it is unsupported by the passage? i initially chose this one because i think the excessive nerve cells will die out, but i think the problem is, we don't know how they die: they can either die due to the absence of NGF, or the presence of anti-NGF. am i correct about this point?

Many thanks!

[ohthatpatrick]

Yeah, I think you mostly nailed it. We don't know how those excess nerve cells die. Maybe NGF is lacking; maybe they encounter anti-NGF antibodies.

(A) actually sounds to me like the excess nerve cells commit suicide ... since it's saying that the excess nerve cells (which need NGF to sustain their survival) actually produce anti-NGF antibodies (which kill the NGF-dependent nerve cells).

We certainly don't have info that allows us to infer that these extra nerve cells produce the substance that kills them off.

[AliceJ612]

Could someone explain why D is wrong?

[echoe427]

Question Type: MSS

Answers are mostly based on line 51-59 of the passage.

(A) is wrong because anti-NGF or lack of NGF both cause suppress the growth.
(B) is wrong because nerve cells don't grow in the absence of NGF, they die if the factor is not present
(C) Maybe fewer, maybe all of them that connected with target cells are needed. The passage does not explicitly say so.
(D) Not mentioned in the passage.
(E) Because NGF stimulates the developing nerve processes toward the correct, specific "target" cells with which they must connect. Read between the lines, it means nerve cells connected to the target cells, NGF helps their continued survival; those that are not connected to the target cells and die in the lack of NGF. Line 57 illustrates this model with an example. Nerve cells affected by NGF grow outside of the brain and spinal cord (which is not connected to the particular targeted cells) die also.