2007-June-2-14

mygoalusa

A cup of raw milk, after being heated in a microwave oven to 50 degrees C, contains half its initial concentration of a particular enzyme, lysozme. If, however, the milk reaches that temperature through exposure to a conventional heat source of 50 C, it will contain nearly all of tis initial concentration of the enzyme. Therefore, what destroys the enzyme is not heat but, microwaves, which generate heat.

Which one seriously weakens the argument?

A. Heating raw milk in a microwave oven to 50 degrees C destroys nearly all of the lysozyme initially presen in that milk

B. Enzyme in raw milk that are destroyed through excessive heating can be replaced by adding enzymes that have been extracted from other source

C. A liquid exposed to conventional heat source of 50 degrees C will reach that temperature more slowly than it would if it were exposed to a conventional heat source hotter than 50 C

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 conventioinal 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


A is strengthen.
B does not weaken, not relevant to conclusion
C both senario relate to conventional heating, not address microwave heating, does not weaken
D taste is irrelevant here
E is the right answer, but I don't understand why it weakens the conclusion
 

sanantonioli

Therefore, what destroys the enzyme is not heat but, microwaves, which generate heat。我的理解是，结论建立的前提之一是被加热到的温度是相同的：50 C。E 指出实际上微波炉加热到的温度更高。

mygoalusa

首先多谢答复,但是根据你的理解,不是strengthen吗?

jane1109

the answer is E, 'cause it is stating an alternative possiblity; the "microwave" does not kill these enzymes, the hotter temperature does. The temp, when heating by the microwave, the temperature actually goes above 50 C, thus killing the enzymes. Remember, this is just providing alternative possiblity, you don't have to prove a conclusion to be false in a weakening question, just make it less believable.

rosemsem

you have to distinguish between microwave and heat.

microwave oven itself does not kill the enzyme. it's the HEAT generated by microwave over does. that's why this weakens the arguement that 'heat' does not kill.