阅读理解。 Is a recently discovered hormone the reason why folks who lose weight can't keep it off? Like millions of other fat people, at 530 inches high, more than 300 pounds, Carnie Wilson was not just fat. After trying all sort of diets that didn't work, she had to go to the stomach-bypass surgery (胃部迂回手 术), ie, have most of her stomach sewed up, only leaving tiny room to hold several tablespoonfuls at most. Result: she simply couldn't eat the way she used to. In three years, Wilson is one third of her former weight. Wilson's experience is not all that unusual, and while doctors still aren't exactly sure what is going on, a report in last week's Journal of Medicine offers an explanation. The loss of appetite in bypass patients may be linked to a recently discovered hormone called ghrelin. Not only that, ghrelin may turn out to be one reason we feel hungry and it's hard for dieters to keep weight off. Nowadays, researchers are careful to stress only what they know for sure. For the three conclusions, the leading Dr. David of the University of Washington says, 'I feel very solid about two of them.' The first is that ghrelin levels in the bloodstream rise significantly before meals and drop afterward. The second conclusion is that ghrelin levels are higher on average in people who have lost weight from dieting. Dr. David is less sure of the third conclusion, that bypass patients have only a quarter as much ghrelin as most people of normal weight. After all, ghrelin is produced by cells in the stomach Years ago, leptin, a hormone was found as an appetite suppressant (食物抑制剂). But after years of trying, it had to be given up. What doctors suspect is that both leptin and ghrelin are part of a complex system of brain and body chemicals that govern weight and appetite. That does not mean pharmaceutical (药物的) weight control is forever out of the question. 'In the next ten years, we will be able to develop new drugs to help people lose weight healthily and effectively.' 1. What can we learn about ghrelin according to the passage? [     ] A. After meals ghrelin levels are higher in the bloodstream. B. People who have lost weight have less ghreilin in their body. C. Without ghrelin, people are really difficult to lose weight. D. Ghrelin is something produced by cells in the stomach. 2. What is Dr. David not sure? [     ] A. Pharmaceutical weight control is impossible. B. There is less ghrelin in the bypass patients. C. New drugs will be developed in 10 years. D. Ghrelin levels are higher in people on diet. 3. In fact, people's weight and appetite are controlled by _____. [     ] A. ghrelin and leptin B. hormone and medicine C. brain and body chemicals D. stomach and food 4. What can we infer from the passage? [     ] A. People with a lower ghrelin level go hungry easily. B. Doctors managed to use leptin to control the appetite. C. Doctors are optimistic about how to lose weight healthily. D. The loss of appetite in bypass patient is linked to leptin.