The main point of the passage is that serotonin is part of the explanation for how the brain knows when carbohydrates have been or should be consumed. The author presents us with a series of facts based on tests done on rats where these rats are given drugs that selectively facilitate serotonin-mediated neurotransmission and drugs that block serotonin-mediated neurotransmission.
(A) is incorrect because the author is not defending a point of view. She is merely explaining a set of facts.
(B) is incorrect because there is no misconception mentioned in the passage.
(C) is incorrect because we are not presented with conflicting evidence.
(D) is incorrect because the tests mentioned in the passage all go in one specific direction. Drugs that either facilitate or block serotonin-mediated neurotransmission are given to rats and humans to see what effect they have on the brain's desire for carbohydrates. No new directions for investigation are mentioned.
(E) is CORRECT because this is exactly what the purpose of the author is. She presents us with information that helps us explain the phenomenon of how the brain knows when carbohydrates have been or should be consumed.
Hope that helps! Let us know if you have any other questions!
@chris_vaAugust 15, 2019
I chose E, but only because I couldn't pull the trigger on D. I thought it might be D because of the last sentence, that possibly this was the underlying focus of the research, suggesting other effects that may be useful indicators. Could you give me an example of if that was the case how it might be worded. Or was there simply not enough in the passage to correlate that statement with actual intent? Thank you. Hope that is a clear question.
