Critical Reasoning

4. Galanin is a protein found in the brain. In an
experiment, rats that consistently chose to eat fatty
foods when offered a choice between lean and fatty
foods were found to have significantly higher
concentrations of galanin in their brains than did rats
that consistently chose lean over fatty foods. These
facts strongly support the conclusion that galanin
causes rats to crave fatty foods.
Which one of the following, if true, most supports the
argument?
(A) The craving for fatty foods does not invariably
result in a rat’s choosing those foods over
lean foods.
(B) The brains of the rats that consistently chose to
eat fatty foods did not contain significantly
more fat than did the brains of rats that
consistently chose lean foods.
(C) The chemical components of galanin are
present in both fatty foods and lean foods.
(D) The rats that preferred fatty foods had the
higher concentrations of galanin in their
brains before they were offered fatty foods.
(E) Rats that metabolize fat less efficiently than do
other rats develop high concentrations of
galanin in their brains.