Reviewer: The author of a recent book argues that lead contributed to

Question

Reviewer: The author of a recent book argues that lead contributed to many public health problems in the late nineteenth and early twentieth centuries. He claims that the main sources of this pollutant were urban water-delivery systems, which used lead pipes that leached lead into the water supply. But my own research on municipalities that used lead pipes during the period in question has shown that the inhabitants of several of them did not exhibit symptoms of lead poisoning, so the pipes are most likely not the primary culprit.

Which of the following would, if true, most weaken the reviewer's reasoning?

(A) In certain areas, exposure to hard water--water with a high mineral content--promotes the formation of a protective coating on the interior of lead pipes.
(B) In the late nineteenth and early twentieth centuries, many household fixtures and consumer products contained lead.
(C) Lead was introduced into gasoline in the 1920s, during which time lead-poisoning symptoms increased in many locales.
(D) Several cities that used lead pipes exhibited unusual rates of convulsive disorders and other conditions associated with lead exposure.
(E) The author in question notes that other factors, including inadequate sewer systems and urban crowding; caused widespread outbreaks of infectious diseases.

pappal · Answer

P1. Author argues--lead main contributor -- serious health problems --19th and 20th centuries-- through urban water delivery systems
P2.reviewer's study of such municipalities --lead poisoning symptoms not found in inhabitants
C. these pipes were not primary culprits
---weakens the conclusion?
1. supports conclusion-- if protective coating is formed by hard water then certainly pipes are not the primary culprit
2. also supports conclusion--gives other causes through lead poisoning would have spread primarily
3.irrelevant-- as discusses the later era than covered in the argument
4.directly most supports that pipes were the main culprits
5.out of scope --as discusses about infectious diseases
so D IMO

anurag029 · Answer

I selected option A because it provides a compelling counterargument to the reviewer's claim that the lead pipes are not a cause of lead poisoning.

abhishkl · Answer

The reviewer concludes that "Lead pipes are not the primary culprit."
Let's consider A: If A is true, then it supports the fact that people will not exhibit symptoms even with lead pipes, which also means that hard water is the reason that these people are not getting affected. Otherwise, they would be affected by lead. That's why this option weakens the reasoning. 
D: "Several" in GMAT means 3 or more, but not many, so even if this offers a counterargument, it's still not completely sufficient to negate the reasoning.

Reviewer: The author of a recent book argues that lead contributed to

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Reviewer: The author of a recent book argues that lead contributed to

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