CR Weaken type

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CR Weaken type

by Mo2men » Sun Feb 12, 2017 3:45 am
The element ytterbium increases its electrical resistance when subject to high mechanical stresses. This property has made it an indispensable component in a medical tool designed to measure the stress on bones, which can guide physicians in setting broken bones. Unfortunately, ytterbium is rare, found in only a few meager sources around the world. A steep market demand will cause the price to skyrocket, and this technology so helpful to physicians will become unaffordable.

Which of the following, if true, most seriously weakens the argument above?

A) Just one mining company controls all the ytterbium that is imported into the United States, where these medical tools are manufactured.
B) The process of extracting pure ytterbium from its ores, euxenite and xenotime, is very expensive and involves strong acids.
C) Ytterbium is also used as an additive, in small quantities, to stainless steel and solid-state lasers.
D) Some common alloys of tin also increase their electrical resistance under mechanical loads.
E) The largest source of ytterbium is in a relatively remote region of China.

Source: Magoosh

OA:D

Although OA:Dmakes sense, is using the word 'some' make sense here? 'some' means at least one i.e. one ore more. If one source found, does it help weaken the argument? I do not recall in offcial qsource any correct answer with choice with word 'some'

Any Expert to clarify please?

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by DavidG@VeritasPrep » Sun Feb 12, 2017 4:44 am
Mo2men wrote:The element ytterbium increases its electrical resistance when subject to high mechanical stresses. This property has made it an indispensable component in a medical tool designed to measure the stress on bones, which can guide physicians in setting broken bones. Unfortunately, ytterbium is rare, found in only a few meager sources around the world. A steep market demand will cause the price to skyrocket, and this technology so helpful to physicians will become unaffordable.

Which of the following, if true, most seriously weakens the argument above?

A) Just one mining company controls all the ytterbium that is imported into the United States, where these medical tools are manufactured.
B) The process of extracting pure ytterbium from its ores, euxenite and xenotime, is very expensive and involves strong acids.
C) Ytterbium is also used as an additive, in small quantities, to stainless steel and solid-state lasers.
D) Some common alloys of tin also increase their electrical resistance under mechanical loads.
E) The largest source of ytterbium is in a relatively remote region of China.

Source: Magoosh

OA:D

Although OA:Dmakes sense, is using the word 'some' make sense here? 'some' means at least one i.e. one ore more. If one source found, does it help weaken the argument? I do not recall in offcial qsource any correct answer with choice with word 'some'

Any Expert to clarify please?
The key weird here is "common." You're right that "some" means "at least one," but even if there is only one common alloy of tin that performs the same function as ytterbium, if that one alloy is common, and, by definition, easily accessible, then it's probably going to represent a viable lower cost alternative. If product x and product y both do the same thing, and one is more expensive than the other, it stands to reason that enough customers will go for the cheaper version that the price of the more expensive one will not spike in response to increasing demand.
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by GMATGuruNY » Sun Feb 12, 2017 4:53 am
Mo2men wrote:The element ytterbium increases its electrical resistance when subject to high mechanical stresses. This property has made it an indispensable component in a medical tool designed to measure the stress on bones, which can guide physicians in setting broken bones. Unfortunately, ytterbium is rare, found in only a few meager sources around the world. A steep market demand will cause the price to skyrocket, and this technology so helpful to physicians will become unaffordable.

Which of the following, if true, most seriously weakens the argument above?

A) Just one mining company controls all the ytterbium that is imported into the United States, where these medical tools are manufactured.
B) The process of extracting pure ytterbium from its ores, euxenite and xenotime, is very expensive and involves strong acids.
C) Ytterbium is also used as an additive, in small quantities, to stainless steel and solid-state lasers.
D) Some common alloys of tin also increase their electrical resistance under mechanical loads.
E) The largest source of ytterbium is in a relatively remote region of China.
Premise: When subject to high mechanical stresses, ytterbium increases its the electrical resistance, a property necessary for an important medical tool.
Conclusion: Because ytterbium is rare, market demand will cause its price to skyrocket, making the medical tool unaffordable.

The correct answer must WEAKEN the conclusion that market demand will cause the price of ytterbium to skyrocket, making the medical tool unaffordable.

D: Some common alloys of tin also increase their electrical resistance under mechanical loads.
Here, at least one other COMMON alloy can serve as a substitute for ytterbium -- since it exhibits the same indispensable property as ytterbium -- WEAKENING the conclusion that market demand for ytterbium will cause its price to skyrocket.

The correct answer is D.

Generally, some is to be avoided in weaken CRs, since some means at least one -- and at least one of something will typically be insufficient to weaken a conclusion.
This CR is an exception.
Here, the existence of even one COMMON alloy that exhibits the same property as ytterbium is sufficient to weaken the conclusion that the price of ytterbium will skyrocket.
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