河北省定州中学2016-2017学年高一（承智班）下学期英语周练试题（4.9）

百强校河北定州中学2016-2017学年第二学期高一承智班英语周练试题（4.9） 一、阅读理解 Smoking is harmful. But as soon as you quit the habit, everything will be OK, right? Wrong. New research has found that even if you give up smoking, the damage it has done to your genes (基因) will stay there for a much longer time. In the research, a team of US scientists studied the blood of 16,000 people. Among them, some were smokers, some used to smoke, and the rest were non-smokers. Scientists compared their genes and found that more than 7,000 genes of smokers had changed-a number that is one-third of known human genes. According to NBC News, both heart disease and cancer are caused by genetic changes. Some people may have had the changes when they were born, but most people get them in their day-to-day lives while doing things like smoking. When you stop smoking, a lot of these genes will return to normal within five years. This means your body is trying to heal (治愈) itself of the harmful effects of smoking. But the changes in som