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Walking, if you do it vigorously enough, is the overall best exercise for regular physical activity. It requires no equipment, everyone knows how to do it and it carries the (1) risk of injury. The human body is designed to walk. You can walk in parks or along a river or in your neighborhood. To get (2) benefit from walking, aim for 45 minutes a day, an average of five days a week.Strength training is another important (3) of physical activity. Its purpose is to build and (4) bone and muscle mass, both of which shrink with age. In general, you will want to do strength training two or three days a week, (5) recovery days between sessions.Finally, flexibility and balance training are (6) important as the body ages. Aches and pains are high on the list of complaints in old age. The result of constant muscle tension and stiffness of joints, many of them are (7) , and simple flexibility training can (8) these by making muscles stronger and keeping joints lubricated (润滑). Some of this you do whenever you stretch. If you watch dogs and cats, you’ll get an idea of how natural it is. The general (9) is simple: whenever the body has been in one position for a while, it is good to (10) stretch it in an opposite position.A．allowingB．avoidableC．brieflyD．componentE．determinedF．helpingG．increasinglyH．lowestI．maintainJ．maximumK．preventL．principleM．provokeN．seriouslyO．topic （3）处应填（）

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With the world’s population estimated to grow from six to nine billion by 2050, researchers, businesses and governments are already dealing with the impact this increase will have on everything from food and water to infrastructure (基础设施) and jobs. Underlying all this (1) will be the demand for energy, which is expected to double over the next 40 years.Finding the resources to meet this demand in a (2) sustainable way is the cornerstone (基石) of our nation’s energy security, and will be one of the major (3) of the 21st century. Alternative forms of energy—bio-fuels, wind and solar, to name a few—are 4 being funded and developed, and will play a growing (5) in the world’s energy supply. But experts say that, even when (6) , alternative energy sources will likely meet only about 30% of the world’s energy needs by 2050.For example, even with (7) investments, such as the ＄93 million for wind energy development (8) in the American Recovery and Reinvestment Act, important alternative energy sources such as wind and bio-fuels (9) only about 1% of the market today.Energy and sustainability experts say the answer to our future energy needs will likely come from a lot of (10) —both traditional and alternative.A．stableB．solutionsC．significantD．roleE．progressF．marvelousG．includedH．growthI．exactlyJ．consistK．compriseL．competitionsM．combinedN．challengesO．certainly （2）处应填（）

假设有下列程序段： For i=1 To 3 For j=5 To 1 Step-1 Print ij Next j Next i 则语句Print ij的执行次数是，i的值为，J的值为__。

The popular notion that older people need less sleep than younger adults is a myth, scientists said yesterday.While elderly people (1) to sleep for fewer hours than they did when they were younger, this has a(n) (2) effect on their brain’s performance and they would benefit from getting more, according to research.Sean Drummond, a psychiatrist (心理医生) at the University of California, San Diego, said that older people are more likely to suffer from broken sleep, while younger people are better at sleeping (3) straight through the night.More sleep in old age, however, is (4) with better health, and most older people would feel better and more (5) if they slept for longer periods, he said."The ability to sleep in one chunk (整块时间) overnight goes down as we age but the amount of sleep we need to (6) well does not change," Dr Drummond told the American Association for the Advancement of Science conference in San Diego."It’s (7) a myth that older people need less sleep. The more healthy an older adult is, the more they sleep like they did when they were (8) . Our data suggests that older adults would benefit from (9) to get as much sleep as they did in their 30s. That’s (10) from person to person, but the amount of sleep we had at 35 is probably the same amount as we need at 75."A．alertB．associateC．attractingD．clingE．continuingF．definitelyG．differentH．efficientlyI．formallyJ．functionK．mixedL．negativeM．sufficientN．tendO．younger （1）处应填（）

数据库系统的主要特点为数据集成性、数据的高______和低冗余性、数据独立性，以及数据统一管理和控制。