单项选择题 根据下列文章,请回答 16～22 题。 Sleeping People who sleep for more than eight hours a night do not live as long as those who sleep for Six hours，according to the biggest study yet into sleep patterns and mortality（死亡率）。Scientists have no explanation for the findings and do not know if they mean people who like a lie-in（睡懒觉）can extend their lives by sleeping less.Although it is a common I belief that sleeping for at least eight hours a night is vital for health and well-being，the six-year study involving more than l.1 million Americans Older than 30 found that those who slept for less than eight hours were far from doing themselves any long-term harm'Individuals who now average 6.5 hours of sleeps a night can be reassured that this is a safe amount of sleep. From a health standpoint，there is no reason to sleep longer，' said Daniel Kripke，a professor of psychiatry（精神病学）at the University of California San Diego.Dr.Kripke said，''We don't know if long sleep periods lead to death. Addition al Studios are needed to determine if setting your alarm clock earlier will actually improve your health.' l he scientists who were funded by the American Cancer Society，found that the best survival rates were among the men and women who slept for seven hours a night. 1 hose who slept for eight hours were 12 per cent more likely to die during the six-year period of the study，when other factors such as diet and smoking were taken into account.Even those who spent a mere five hours a night in bed lived longer than those who slept eight or more hours. However，an increasing death rate was found among those who slept for less than five hours. Dr.Kripke said，'Previous sleep studies have indicated that both short-and long-duration（持续时间）sleep had higher mortality rates-However-none of those studies was large enough to distinguish the difference between seven and eight hours a 1night.Until now' 第 16 题 More than one million Americans participated in the six-year study.A．RightB．WrongC．Not mentioned

填空题 对飞机的飞行速度进行15次独立试验，测得飞机的最大飞行速度(单位：m／s)如下： 422．2 418．7 425．6 420．3 425．8 423．1 431．5 428．2 438．3 434．0 41 2．3 417．2 413．5 441．3 423．7 根据长期经验，可以认为最大飞行速度服从正态分布，试求最大飞行速度期望值的置信区间．(置信度为95％)（）

单项选择题 根据下列文章,请回答 23～30 题。 The Drink Your Body Needs Most 1 0UF bodies are estimated to be about 60 to 70%water. Blood is mostly water. and our muscles，lungs，and brain all contain a lot of water. Water is needed to regulate body temperature and to provide the means for nutrients（滋养物）to travel to all our organs. Water also transports oxygen to our cells，removes waste，and protects our joints and Organs. 2 We lose water through urination（排尿），respiration（呼吸），and by sweating. If you are very active you lose more water than if you do not take much exercise. Symptoms of mild dehydration（脱水）include chronic pains in joints and muscles，lower back pain，headaches，and constipation（便秘）。A strong smell to your urine，along with a yellow color indicates that you are not geeing enough water. Thirst is an obvious sign of dehydration and in fact. You need water long before you feel thirsty. 3 A good rule of thumb（好的做法）is to take your body weight in pounds and divide that number in half. That gives you the number of ounces（盎司）of water per day that you need. For example，if you weigh 160 pounds，you should drink at least 80 0unces of water per day.1f you exercise you should drink another 8-ounce glass of water for every 20 minutes you are active. If you drink coffee or alcoh01.you should add at Least an equal amount of water. When you are traveling on an airplane it is good to have 8 0unces of water for every hour you are on board the plane. 4 It may be difficult to drink enough water on a busy day. Be sure you have water handy at all times by keeping a bottle for water with you when you are workin9，traveling，or exercisin9.If you get bored with plain water，add a bit of lemon for a touch of flavor. There are some brands of flavored water available. but some of them have sugar or artificial sweeteners that you don't need. 第 23 题 Paragraph 1____________