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? ['The chemical components of galanin are present in both fatty foods and lean foods.', 'The rats that preferred fatty foods had the higher concentrations of galanin in their brains before they were offered fatty foods.', 'Rats that metabolize fat less efficiently than do other rats develop high concentrations of galanin in their brains.', '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.']