Passage

The answer to this question is found in lines 11-14: "drugs that block serotonin . . . often induce carbohydrate craving." See also lines 32-34 ("the level of serotonin in the brain in turn affects the amount of carbohydrate an individual chooses to eat") and lines 41-44 ("on the other hand, when rats are given drugs that interrupt serotonin-mediated neurotransmission, their brains fail to respond when carbohydrates are eaten, so the desire for them persists"). Hope this helps! Please let us know if you have any additional questions.

Why is A correct if "protein-rich snacks" aren't mentioned?

Protein is not mentioned in the passage, so why protein mentioned in the answer choices?

Hi, (A) is correct because the "protein-rich snacks" are just cited as opposed to a carbohydrate-rich food, and we're supposed to know that the rats will spring more for carbohydrates. Hope this helps!