题目内容
A Thirsty World
The world is not only hungry, it is also thirsty for water. This may seem strange to you, since nearly 75% of the earth's surface is covered with water. But about 97% of this huge amount is sea-water, or salt water. Man can only drink and use the other 3%-the fresh water that comes from rivers, lakes, underground, and other sources. And we cannot even use all of that, because some of it is in the form. of icebergs (冰山) and glaciers (冰川). Even worse, some of it has been polluted.
At the moment, this small amount of fresh water is still enough for us. However, our need for water is increasing rapidly. Only if we take steps to deal with this problem now can we avoid a severe worldwide water shortage later on. A limited water supply would have a bad effect on agriculture and industry.
In addition to stopping wasting our precious water, one useful step we should take is to develop ways of reusing it. Experiments have already been done in this field, but only on a small scale.
Today, in most large cities, water is used only once. and it eventually returns to the sea or runs into underground storage tanks. But it is possible to pipe water that has been used to a purifying (净化) plant. There it can be filtered (过滤) and treated with chemicals so that it can be used again just as if it were fresh from a spring.
But even if every large city purified and reused its water, we still would not have enough. Where could we turn next？ To the oceans! All we'd have to do to make use of the vast amount of sea-water is-remove the salt. This salt-removing process is already in use in many parts of the world.
So if we take all these steps, we'll be in no danger of drying up!
The phrase "the world" in the first line of the passage refers to
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Video recorders and photocopiers, even ticket machines on the railways, often seem unnecessarily difficult to use. Last December I bought myself a video cassette recorder (VCR) described as "simple to use". In the first three weeks I failed repeatedly to program the machine to record from the TV, and after months of practice I still made mistakes. I am not alone. According to a survey last year by Ferguson, the British manufacturer, more than one in four VCR owners never use the timer on their machines to record a program: they don't use it because they've found it far too hard to operate.
So why do manufacturer keep on designing and producing VCRs that are awkward to use if the problems are so obvious？ First, the problems we notice are not obvious to technically minded designers with years of experience and trained to understand how appliances work. Secondly, designers tend to add one or two features at a time to each model, whereas you or I face all a machine's features at once. Thirdly, although finding problems in a finished product is easy, it is too late by then to do anything about the design. Finally, if manufacturers can get away with selling products that are difficult to use, it is not worth the effort of any one of them to make improvements.
Some manufacturers say they concentrate on providing a wide range of features rather than on making the machines easy to use. But that gives rise to the question, "Why can't you have features that are easy use？" The answer is you can.
Good design practice is a mixture of specific procedures and general principles. For a start, designers should build an original model of the machine and try it out on typical members of the public—not on colleagues in the development laboratory. Simple public trials would quickly reveal many design mistakes. In an ideal world, there would be some ways of controlling quality such as that the VCR must be redesigned repeatedly until, say, 90 percent of users can work 90 per cent of the features correctly 90 per cent of the time.
The author had trouble operating his VCR because______.
Are You a Man or a Mouse？
Are you a man or a mouse？ When people ask this question they want to know if you think you are a brave person or a coward (懦夫). But you will never really know the answer to that question until you are tested in real life. Some people think they are brave, but when they come face to face with real danger, they act like cowards. Other people don't think of themselves as brave, but when they meet danger, they act like heroes.
Lenny Brown had always thought of himself as a nervous person. He got worried before examinations. He worried about his job and his health. All he wanted in life was to be safe and healthy.
On 15 January 1982, a plane crashed into the Potomac River in Washington. Lenny went to the river to see what was happening. Then he saw a woman in the ice-cold water. Suddenly Lenny did not feel afraid. He kept very calm and did a very brave thing. He jumped into the river, swam to the woman, and kept her head above the water. Seventy-eight people died that day. Thanks to Lenny Brown, it was not seventy-nine.
When you are in a very dangerous situation and feel afraid, the body automatically produces a chemical in the blood. This chemical is called adrenalin (肾上腺素). With adrenalin in the blood system, you actually feel stronger and are ready to fight or run away. However, when you are absolutely scared, the body can produce too much adrenalin. When this happens, the muscles (肌肉) become very hard and you find that you cannot move at all: you are filled with fear. That is why, when we are very frightened, we sometimes say that we are "like a stone".
The question "Are you a man or a mouse？" really means to ask whether you believe
有一两跨四层框架，梁、柱现浇，楼盖为装配式楼盖。梁的跨度为6m，混凝土强度等级为C30，受力纵筋为HRB335，箍筋为HPB235。屋面梁b=300mm，h=500mm，顶层柱b=400mm，h=400mm，梁的混凝土护层厚度为25mm，柱的混凝土保护层厚度为30mm，层高H=4.5m。
以下程序的输出结果是 ______。 main() int a=3； printf("%d\n"，(a+=a=a=a*a) ; }
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