|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 circulating sodium level. The students compared wild-type mice and knockout mice, which are mice with specific genes deactivated, when mice of each type were placed in similar naturalistic environments and taken for periodic blood sampling. Finding that knockout mice with the gene Asb5 deactivated tended to have lower concentrations of sodium in their blood than did wild-type mice, the students concluded that differences in circulating sodium level among house mice in nature are solely attributable to variations in the level of expression of Asb5.
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 circulating sodium level but showed a wide variety of levels of expression of Asb5.
A
A sampling of house mice captured in natural settings shows that individual mice can differ from one another in the level of expression of Asb5.
B
The level of expression of Asb5 does not appear to affect the functioning of any other genes in house mice.
C
The mice with Asb5 deactivated were identical to the wild-type mice except with regard to circulating sodium level.
D