For years, Scientists have believed that a certain hormone produced by

I also think, E is the correct answer choice.
For years, Scientists have believed that a certain hormone produced by the human liver was triggered by enzyme U, which is released in the pancreas. Recently, however, researchers in Belgium discovered that Enzyme U is always preceded by the release of Enzyme W in the brain. Based on this, these researchers hypothesize that Enzyme W, not Enzyme U, triggers the production of the liver hormone.
Scientists:-
Liver Hormone precedes by enzyme U.
E(U)=>LH.............(1)
Researchers in Belgium:-
Enzyme U is always preceded by Enzyme W.
E(W)=>E(U) ...................(2)
These Researcher concluded from 1 & 2 that..
E(W)==>LH ..................(3)
They also said that Production of Liver Hormone is independent of Enzyme U.

To weaken the hypothesis i.e. (3), We need to find something that will show that Enzyme U is required and sufficient to produce Liver Hormone AND Enzyme W may not be required.
That is, We need to break the link between (1) and (2).

Only Option (E) does this.

Premise: Enzyme U is preceded by the release of Enzyme W
Conclusion: Enzyme W, not Enzyme U, triggers the production of the liver hormone
What if No enzyme W released, but liver hormone is still produced? ==> E says exactly the same ==> E is correct.

I have this doubt.

We are given this FACT: Researchers in Belgium discovered that Enzyme U is always preceded by the release of Enzyme W in
the brain.

In CR questions we are not allowed to play with the facts.

But in answer choice E this fact is exploited to weaken the conclusion.

If you use the GMATPill CR framework for this question, you'll see that it relates to "exclusive conclusion".

"W" is the sole cause for the liver hormone, and nothing else.

How do we weaken? Well, it's the opposite of the methods we could use to strengthen. If you try to strengthen, you'll notice it uses you can use the "exclusive negation" concept -- so apply that pre-thinking in the opposite way. So you can try:
1) Showing that W was not even present at the time the liver hormone was produced
2) Showing that something other than W may have helped cause the liver hormone to be produced.

Here, the correct answer choices uses the first strategy above to weaken the conclusion.


The short-cut to strengthen is:
"W" --> liver hormone
"something else" did NOT affect liver hormone

The short-cut to weaken is:
"W" completely not related to liver hormone
"something else" DID affect liver hormone.

This strategy utilizes GMATPill CR Framework #4 Exclusive Negation.

Hi prinkashar.

There are some fundamental rules for Weakening questions:
(1) Information in the stimulus is suspect.
(2) Answer choices are accepted as given, even if they include "new" information.

Do not assume Fact in the weakening is always true. When you solve a weakening questions, always ask yourself:
- Is the information provided in the stimulus correct?
- Is the information provided in the stimulus comprehensive? (to solve representative questions)
- The comparison in the stimulus correct?
- Will the conditions leading to the conclusion happen or NOT?

Back to the question, there are not any rules that require the fact in the weakening question be ALWAYS true. Don't be confused with "must be true" or "main point" questions that require all answers choices pass the FACT TEST.

Hope it clears your doubt.

KAPLAN OFFICIAL EXPLANATION:

Here's an example of a typical GMAT-style study. We're asked to find a set of results that would weaken a particular hypothesis, so the first thing to do is to locate and understand the hypothesis. It's tough to know at this point whether the weakener will simply offer some kind of proof against the hypothesis, or whether it will call attention to an assumption necessary for the hypothesis to hold. The Belgian researchers maintain that, since Enzyme U is always preceded by the release of Enzyme W, it must be Enzyme W, as opposed to U, that triggers the release of the liver hormone. Since the researchers argue that Enzyme W triggers the release of the liver hormone, in order to weaken this argument we can look for evidence either of another cause or of a situation in which the liver hormone appears in the presence of Enzyme U without Enzyme W. Choice (E) directly counters the hypothesis by providing an example of the effect without the supposed cause. If the release of Enzyme U is followed by the production of the liver hormone, even though Enzyme W was not released, then that hammers the researchers' conclusion that Enzyme W is responsible for the hormone.

(A) strengthens, rather than weakens, the causal link between Enzyme W and production of the liver hormone. This choice provides an exact confirmation of what the researchers would predict.

(B) strengthens part of the hypothesis—the part that claims that Enzyme U does not trigger the production of the hormone—although it mentions nothing about W. It also contradicts the notion that U is always preceded by W, but does nothing to weaken the major hypothesis that W triggers the liver hormone.

(C) is perfectly consistent with the hypothesis: Without W, the researchers would not expect the liver hormone to be produced.

An 800 test taker can recognize statements that are perfectly consistent with a set of facts.

(D) represents exactly what we'd expect to happen if the hypothesis were true, so it's clearly not the weakener we seek.

No doubt you noticed the element of causation here—the study centers around a fairly textbook case of cause-and-effect. As you'll see, the logical elements presented thus far rarely occur in isolation. So let's take stock of where we are, and then move on to questions that combine the various features highlighted in the previous questions.

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