vomhorizon
A cup of raw milk, after being heated in a microwave oven to 50 degrees Celsius, contains half its initial concentration of a particular enzyme, lysozyme. If, however, the milk reaches that temperature through exposure to a conventional heat source of 50 degrees Celsius, it will contain nearly all of its initial concentration of the enzyme. Therefore, what destroys the enzyme is not heat but microwaves, which generate heat.
Which one of the following, if true, most seriously weakens the argument?
(A) Heating raw milk in a microwave oven to a temperature of 100 degrees Celsius destroys nearly all of the lysozyme initially present in that milk.
(B) Enzymes in raw milk that are destroyed through excessive heating can be replaced by adding enzymes that have been extracted from other sources.
(C) A liquid exposed to a conventional heat source of exactly 50 degrees Celsius will reach that temperature more slowly than it would if it were exposed to a conventional heat source hotter than 50 degrees Celsius.
(D) Milk that has been heated in a microwave oven does not taste noticeably different from milk that has been briefly heated by exposure to a conventional heat source.
(E) Heating any liquid by microwave creates small zones within it that are much hotter than the overall temperature that the liquid will ultimately reach.
Source: LSAT
"The argument contains causal reasoning, because the conclusion attempts to attribute a phenomenon (difference in concentration of lysozyme) to a particular cause—microwaves:
Premise: When you heat raw milk in a microwave to 50'C, it contains half of its initial concentration of lysozyme.
Premise: When you heat raw milk on the stove to 50'C, it contains nearly all of its initial concentration of lysozyme.
Conclusion: Microwaves (cause) Destroy lysozyme (effect)
As with many causal arguments, this one ignores the possibility of an alternative cause. What if the depletion of lysozyme has nothing to do with microwaves? Maybe microwaves do something else to the milk that destroys its lysozyme?
Answer choice (A) is incorrect, because it is consistent with the information in the stimulus. If heating the milk to 50'C destroys half of the lysozyme, it's possible that heating it to a boiling temperature would destroy all of it. There is no reason to believe that this would weaken the argument.
Answer choice (B) is incorrect, because the issue is not whether the lost enzymes can be replaced, but rather why they are lost in the first place.
Answer choice (C) is incorrect, because it only stands to reason that liquids heat up faster when exposed to higher temperatures. This does not explain the difference in the amount of lysozyme observed.
Answer choice (D) is incorrect, because the issue of taste has no bearing on the conclusion of the argument. The question is why microwaved milk has less lysozyme than milk exposed to conventional heat source, not whether this difference affects taste.
Answer choice (E) is the correct answer choice. If heating milk by microwave creates small zones within it that are much hotter than 50'C, then it stands to reason that these pockets will lose lysozyme at a higher rate than the rest of the milk. So, although the overall temperature reached is ultimately 50'C, some of the milk will have been exposed to much higher temperatures, which could have caused its enzymes to break down."
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https://forum.powerscore.com/lsat/viewtopic.php?t=11057)