Which one of the following best states the main idea of the passage A. The body's need for carbohydrates varies with the level of serotonin in the blood. B. The body's use of carbohydrates can be regulated by the administration of serotoninlike drugs. C. The role of serotonin in regulating the consumption of carbohydrates is similar in rats and in humans. D. The body's desire for carbohydrates can be influenced by serotonin or serotoninlike drugs. E. Tryptophan initiates a chain of events that regulates the body's use of carbohydrates.