Chemist: The molecules of a certain weed-killer are always present in

Question

Chemist: The molecules of a certain weed-killer are always present in two forms, one the mirror image of the other. One form of the molecule kills weeds, while the other has no effect on them. As a result, the effectiveness of the weed-killer in a given situation is heavily influenced by which of the two forms is more concentrated in the soil, which in turn varies widely because local soil conditions will usually favor the breakdown of one form or the other. Thus, much of the data on the effects of this weed-killer are probably misleading.

Which one of the following, if true, most strengthens the chemist’s argument?
 
(A) In general, if the molecules of a weed-killer are always present in two forms, then it is likely that weeds are killed by one of those two forms but unaffected by the other.
(B) Almost all of the data on the effects of the weed-killer are drawn from laboratory studies in which both forms of the weed-killer’s molecules are equally concentrated in the soil and equally likely to break down in that soil.
(C) Of the two forms of the weed-killer’s molecules, the one that kills weeds is found in most local soil conditions to be the more concentrated form.
(D) The data on the effects of the weed-killer are drawn from studies of the weed-killer under a variety of soil conditions similar to those in which the weed-killer is normally applied.
(E) Data on the weed-killer’s effects that rely solely on the examination of the effects of only one of the two forms of the weed-killer’s molecules will almost certainly be misleading.

Source: LSAT

ShitakeMushroom · Answer

I answered E.

From the argument, I understand that the soil will remain only one form of the weed-killers, so much of the data on the effects of this weed-killer are probably misleading. Choice E which says that data on the weed-killer’s effects that rely on one form will almost certainly be misleading will strengthen the conclusion of argument.

Could someone help explain it?

Could someone help explain it?
Thanks in advance.

Saps · Answer

B it is. I solved it by eliminating.

A - "In general" is not definite
C and D, supports, but does not provide definite support on both (about 2 diff type of molecule) types of claims made by chemist.
E - Irrelevant.

B is the only one, which provided data: that in lab, the experiments conducted used soil with equal concentration of both type of molecule and with no discrimination in conditions for breaking of both molecule. Hence if one type of molecule break fast and only the other has high concentration left, this will impact weed killing. Which is the same as what author mentioned. Hope this helps.

exc4libur · Answer

recap: argument is that w-killer data is misleading, because the soil determines the final concentration of the molecule that, in turn, determines the w-killer's effects; 
query: why (B)?

GMATNinja · Answer

The chemist's conclusion, indeed, is that  much of the data on the effects of this weed-killer are probably misleading.

Here's how the chemist reaches this conclusion:

The weed-killer's molecules are always present in two forms (let's say X and Y). 
  X kills weeds. Y has no effect on weeds. 
  As a result, the effectiveness of the weed-killer is heavily influenced by whether X or Y is more concentrated in the soil. 
  Local soil conditions usually favor the breakdown of X or Y. 
  So the concentration of X or Y in soil varies widely from one situation to the next. 
  Therefore, much of the data on the effects of this weed-killer are probably misleading.

Notice that the chemist's conclusion is about  data  on the effects of this weed-killer.. but NOTHING else in the chemist's argument mentions this data, or where it comes from. Instead, the argument tells us about the behavior of the weed killer's two molecular forms, then explains what happens to those forms in local soil conditions.

As we review the answer choices to determine which one most strengthens the argument, let's keep that in mind.

Choice (A) basically restates what we already know, and tells us nothing about the data in question. Eliminate it.

Whoa, we've hit paydirt (pun definitely intended)! Choice (B) fills our missing information gap by telling us that almost all of this data comes from lab studies where X and Y are  equally concentrated and equally likely to break down in the soil . This confirms that the data in question does not represent how this weed-killer actually shows up, and how it actually breaks down, in a given situation.

If this data is not representative of the real world, then the chemist's argument is definitely stronger. We keep (B) around because it completes the chemist's explanation of why much of this data is misleading.

Choice (C) tells us nothing about the data being questioned by the chemist. Eliminate it.

If this were true, then the author's conclusion would be less convincing. Choice (D) confirms that the data reflect real-world conditions, which gives us less reason to doubt the data — and this weakens the chemist's argument. That's why we eliminate (D).

Choice (E) describes one type of data: data that rely solely on the examination of the effects of just X or just Y. But is this the data that the chemist is referring to when they conclude that "much of the data on the effects of this weed-killer is probably misleading"? And if it is, how much does this particular type of data represent the greater set of data on the effects of this weed-killer?

Unfortunately, we have no way of knowing based on the passage and the information in this answer choice. So while choice (E) introduces some doubt, choice (B) still does much more to strengthen the chemist's argument.

And remember, we're supposed to keep the answer choice that, if true,  most strengthens the chemist's argument . That's why we eliminate (E) and keep (B).

I hope this (um, dive into the logical weeds?) helps!

VerbalBot · Answer

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Chemist: The molecules of a certain weed-killer are always present in

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