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.
A. Incorrect. This just reiterates the fact that microwaves can destroy lysozyme. It doesn’t show that heat, rather than microwaves, is the real cause. Since higher temperatures often involve more microwave energy, this doesn’t rule out microwaves as the main factor.
B. Incorrect. While this tells us how to potentially fix the issue caused by microwaving, it doesn’t explain why the lysozyme is being damaged in the first place. It addresses a solution, not the cause.
C. Incorrect. If you chose this, you may have misread it as stating that microwaves heat milk faster than conventional methods. But this option doesn’t say that and offers no relevant information about the actual scenario discussed.
D. Incorrect. This just confirms a basic scientific fact: hotter things heat other objects more quickly. That doesn’t help explain the effect microwaves have on lysozyme, nor does it clarify the cause of the damage.
E. Correct. This supports the idea that microwaves may heat milk to higher temperatures than conventional methods. Since a heat source can't raise something’s temperature beyond its own, this suggests microwaves might be creating higher heat overall—meaning heat, not microwaves themselves, could be what’s damaging the lysozyme.
