|Question 13Verbal

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Students in a biology class investigated why individual house mice (Mus musculus) can differ from one another in their susceptibility to cataracts in old age. The students compared wild-type mice and knockout mice, which are mice with specific genes deactivated, when mice of each type were raised in similar naturalistic environments and periodically tested for cataracts. Finding that knockout mice with the gene Aasdh deactivated tended to develop cataracts more frequently than did wild-type mice, the students concluded that differences in cataract frequency among house mice in nature are solely attributable to variations in the level of expression of Aasdh.
Which finding, if true, would most directly weaken the students' conclusion?
Some wild-type mice were very similar to the knockout mice with regard to cataract frequency but showed a wide variety of levels of expression
A
The level of expression of Aasdh does not appear to affect the functioning of any other genes in house mice.
B
A sampling of house mice captured in natural settings shows that individual mice can differ from one another in the level of expression of Aasdh.
C
The mice with Aasdh deactivated were identical to the wild-type mice except with regard to cataract frequency.
D