The average British people get six-and-a-half hours" sleep a night, according to the Sleep Council. It has been known for some time that the amount of sleep people get has,【C1】______declined over the years. But【C2】______the average amount of sleep we are getting has fallen, rates of obesity and diabetes have soared. Could the two be connected? We wanted to see what the【C3】______would be of increasing average sleep by just one hour. So we asked seven volunteers, who【C4】______sleep anywhere between six and nine hours, to be【C5】______at the University of Surrey"s Sleep Research Centre. The volunteers were randomly【C6】______to two groups. One group was asked to sleep for six-and-a-half hours a night, the other got seven-and-a-half hours. After a week the researchers took blood tests and the volunteers were asked to switch sleep【C7】______. The group that had been sleeping six-and-a-half hours got an【C8】______hour, the other group slept an hour less. Computer tests designed to measure brain wave activity【C9】______that most of them struggled with mental agility tasks when they had less sleep, but the most interesting results came from the blood tests that were【C10】______. Dr Simon Archer and his team at Surrey University were【C11】______interested in looking at the genes that were switched on or off in our volunteers【C12】______changes in the amount that we had made them sleep. "We found that【C13】______there were around 500 genes that were affected," Archer【C14】______. "Some which were going up, and some which were going down." What they discovered is that when the volunteers【C15】______back from seven-and-a-half to six-and-a-half hours" sleep a night, genes that are【C16】______with processes like immune response and response to stress became more【C17】______The team also saw increase in the activity of genes related to diabetes and risk of cancer. The【C18】______happened when the volunteers added an hour of sleep. So the clear【C19】______from this experiment was that if you are getting less than seven hours" sleep a night and can alter your sleep habits, even one hour more, it could make you【C20】______.
单选题
【C1】
【正确答案】
B
【答案解析】解析：下一句的the average amount说明本空格所提到的the amount of sleep为平均睡眠时间，故B项on average“平均”为答案，表示英国人睡眠时间整体的情况。