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阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项中，选出最佳选项。 Researchers have just offered evidence in a study that says obesity appears to spread through social ties, much like a virus. When one person gains weight, their close friends often follow. But the finding might also offer hope. If friends help make obesity acceptable, then might also be influential in losing the fat. The researchers note that support groups are already an effective tool in dealing with other socially influenced problems, like alcoholism. The findings appeared in the New England Journal of Medicine, The researchers used information collected from 12,000 people. It was collected between 1971 and 2003 as part of the Framingham Heart Study. The information was highly detailed. There was even contact information for close friends of the people in the study. The researchers examined more than 40,000 social ties. They found that a person’s chances of becoming severely overweight increased by 57% if a friend had become obese. A sister or brother of a person who became obese had a 40% increased chance of becoming obese. The risk for a wife or husband was a little less than that. Nicholas Christakis of Harvard Medical School was a lead investigator in the study. He says there is a direct causal relationship between a person getting fat and being followed in weight gain by a friend. | 
