A、It may cause diabetes. B、It may lead to weight gain. C、It may trigger heart disease. D、It may ruin the appetite. B短文开头就点明，虽然戒烟

(19)Researchers say the prospect of weight gain makes some smokers reluctant to stop. But they believe quitting has a positive effect on heart risk. The health gains from giving up were most marked in people who did not have diabetes, but people with the condition were still said to have benefited. Obesity is a risk factor in heart disease.(19)Studies suggest people who stop smoking gain on average 6 to 13 pounds over the first six months. So, researchers started to examine whether weight gain might cancel out some of the benefits of quitting smoking. The JAMA research looked at the smoking habits and heart health of more than 3 000 people between 1981 and 2011.(20)Former smokers who had stayed away from tobacco for more than four years had a 54% lower risk of heart disease than smokers. Recent quitters who had stopped smoking for up to four years experienced almost the same benefit with a 53% lower relative risk. Dr. James Meigs is one of the authors of the study at Harvard Medical School. He says that people might experience moderate weight gain. But there is no doubt that stopping smoking has a very positive effect on heart risk for patients. It doesn’t matter whether people have diabetes or not. Doireann Maddock is a senior nurse at the British Heart Foundation.(21)She says if people are worried about gaining weight, aids like gum may help people resist the temptation to reach for comfort food in the place of a cigarette. Therefore, the weight gain should not deter smokers from quitting.
19. What is the negative effect of quitting smoking?
20. What is the finding of the JAMA research?
21. What is the suggestion the senior nurse gives to smokers?