We don't have pre-written explanations for every reading comprehension passage. However, you can click on the speech bubble in the top right corner to see if there have been any discussions about a particular question. If that doesn't give you the information you are looking for, feel free to post a question like you just did. We will respond as soon as possible. I'll go over this question.
"Which one of the following best states the main idea of the passage?"
A. Was the amount of serotonin in the blood relevant to this relationship between carbohydrates and serotonin? I don't believe so. The concentration of tryptophan in the blood was discussed in paragraph two, but tryptophan is not converted into serotonin until it reaches the nervous system. This is the mechanism by which carbohydrate intake affects serotonin levels in the brain. This is why A is incorrect.
B. This one seems like a good option at first, but there is a problem. Is this passage about the body's "use" of carbohydrates or the body's intake of carbohydrates? The main point is about where the desire to eat carbs comes from, so B is incorrect.
C. This may be true, as demonstrated in the third paragraph. However, this is simply information that supports the author's main point. The whole passage is not meant to demonstrate this similarity between rats and humans.
D. This is the correct answer. It includes the desire for carbohydrates, which is established in the first paragraph as the phenomenon that the author is researching. It also includes the role of serotonin and serotonin-like drugs. No main point answer choice would be complete without mentioning serotonin, as the author spends the entire passage discussing this neurotransmitter.
E. No mention of serotonin. No mention of carbohydrate cravings. Incorrect.
