New research has found that even if you give up smoking...

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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 g them,some were smokers,some used to smoke,and the rest were ntists 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 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 means your body is trying to heal（治愈）itself of the harmful effects of the changes in some of the genes stay for can stay for as long as 30 ’s almost like leaving a footprint on wet cement（水泥）一it will always be there, even when you’ve walked away and when the cement becomes dry.

Although the study results may make people unhappy,there is a bright side: the findings could help scientists invent medicine to treat genetic damage caused by smoking or find ways to tell which people have heart disease or cancer ricks.

function of Paragraph 1 is to .

an example oduce the topic of the passage

an argument the main idea of the passage

genetic changes happen because of .

le's condition at birth ronmental pollution

le's bad living habits t disease and cancer

underlined word "it" in Paragraph 6 refers to .

cement footprint harmful genetic change

h of the following statements is true?

findings are the fruit of more than three years' research.

findings have prevented more people from starting smoking.

findings offer evidence that a damaged gene can heal itself.