单选题The author thinks that ______.A packing is actually useless and could be ignoredB people will soon stop using packaging altogetherC enough research has been done into recyclingD it is better to produce new materials than to re-use old ones

题目

单选题

The author thinks that ______.

packing is actually useless and could be ignored

people will soon stop using packaging altogether

enough research has been done into recycling

it is better to produce new materials than to re-use old ones

更多“单选题The author thinks that ______.A packing is actually useless and could be ignoredB people will soon stop using packaging altogetherC enough research has been done into recyclingD it is better to produce new materials than to re-use old ones”相关问题

第1题

共用题干 New Understanding of Natural Silk's MysteriesNatural silk,as we all know,has a strength that man-made materials have long struggled to match.In a discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough,MIT re- searchers have discovered that silk gets its strength from its weakness.Or,more specifically,its many weak- nesses. Silk gets its extraordinary durability and ductility（柔韧性）from an unusual arrangement of hydrogen bonds that are intrinsically very weak but that work together to create a strong,flexible structure.Most materials一especially the ones we engineer for strength一get their toughness from brittleness.As such,natural silks like those produced by spiders have long fascinated both biologists and engineers because of their light weight,ductility and high strength(pound for pound,silk is stronger than steel and far less brittle). But on its face,it doesn't seem that silks should be as strong as they are;molecularly,they are held together by hydrogen bonds , which are far weaker than the covalent（共价的）bonds found in other molecules.To get a better understanding of how silk manages to produce such strength through such weak bonds, the MIT team created a set of computer models that allowed them to observe the way silk behaves at the atomic level. They found that the arrangement of the tiny silk nanocrystals（纳米晶体）is such that the hydro- gen bonds are able to work cooperatively,reinforcing one another against external forces and failing slowlywhen they do fail,so as not to allow a sudden fracture to spread across a silk structure.The result is natural silks that can stretch and bend while retaining a high degree of strength.But while that's all well and good for spiders,bees and the like,this understanding of silk geometry could lead to new materials that are stronger and more ductile than those we can currently manufacture.Our best and strongest materials are generally expensive and difficult to produce(requiring high temperature treatments or energy-intensive processes).By looking to silk as a model,researchers could potentially devise new manufacturing methods that rely on inexpensive materials and weak bonds to create less rigid,more forgiving materials that are nonetheless stronger than anything currently on offer. And if you thought you were going to get out of this materials science story without hearing about carbon nanotubes（纳米碳管）, think again. The MIT team is already in the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural silk-like carbon nanotubes. Super-silks are on the horizon.The MIT team had tried different materials before they studied natural silk in their research.A:RightB:WrongC:Not mentioned

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第2题

Many people use wood stoves and fireplaces to heat their homes．Scientists have become worried about the smoke that they give off．Harmful chemicals are in the smoke．The smoke is causing air pollution．The pieces of pollution,called soot,are floating in the air．They are too tiny to see．Scientists must use a microscope to see them.Small amounts of soot are safe,but large amounts can be dangerous．The govenment wants to limit this kind of pollution．It may stop people from using their fireplaces.The air is tested every day．When soot levels are high,more than 65 micrograms of soot per cubic meter,factories must stop making smoke．The government thinks that limit should be much lower. Factories produce the most smoke and soot．But the government thinks that all types of burning should be limited．The soot levels from factories and homes could be limited．Home owners may have to install new wood stoves that they comply with the new law．Or,they may not be able to bum on days when the air quality is bad.Residents of some towns are fined if they violate the burning ban．Scientists hope these new regulations will make the air cleaner and less harmful to breathe.What could home owners do to comply with the new regulation?A.Write a lette B.Ask for permissio C.Use more electricit D.Install new low-soot fireplace

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第3题

Many people use wood stoves and fireplaces to heat their homes．Scientists have become worried about the smoke that they give off．Harmful chemicals are in the smoke．The smoke is causing air pollution．The pieces of pollution,called soot,are floating in the air．They are too tiny to see．Scientists must use a microscope to see them.Small amounts of soot are safe,but large amounts can be dangerous．The govenment wants to limit this kind of pollution．It may stop people from using their fireplaces.The air is tested every day．When soot levels are high,more than 65 micrograms of soot per cubic meter,factories must stop making smoke．The government thinks that limit should be much lower. Factories produce the most smoke and soot．But the government thinks that all types of burning should be limited．The soot levels from factories and homes could be limited．Home owners may have to install new wood stoves that they comply with the new law．Or,they may not be able to bum on days when the air quality is bad.Residents of some towns are fined if they violate the burning ban．Scientists hope these new regulations will make the air cleaner and less harmful to breathe.What happens to some residents who bum too much wood?A.They could lose their home B.They pay for the punishmen C.They get sick from the smok D.The fire could get out of contro

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第4题

Many people use wood stoves and fireplaces to heat their homes．Scientists have become worried about the smoke that they give off．Harmful chemicals are in the smoke．The smoke is causing air pollution．The pieces of pollution,called soot,are floating in the air．They are too tiny to see．Scientists must use a microscope to see them.Small amounts of soot are safe,but large amounts can be dangerous．The govenment wants to limit this kind of pollution．It may stop people from using their fireplaces.The air is tested every day．When soot levels are high,more than 65 micrograms of soot per cubic meter,factories must stop making smoke．The government thinks that limit should be much lower. Factories produce the most smoke and soot．But the government thinks that all types of burning should be limited．The soot levels from factories and homes could be limited．Home owners may have to install new wood stoves that they comply with the new law．Or,they may not be able to bum on days when the air quality is bad.Residents of some towns are fined if they violate the burning ban．Scientists hope these new regulations will make the air cleaner and less harmful to breathe.Why is it dangerous to burn too much wood?A.The fire could burn yo B.It's not healthy to be too war C.Harmful chemicals are released in the so D.The smoke is filled with un see able tiny piece

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第5题

Construction on a new wing at the Markunas Museum ____as soon as additional funding has been arranged.A.has been resumed B.to be resuming C.was resumed D.will resume

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第6题

Research Is a State of MindFor many years there has been much misunderstanding as to just what research is. The popular conception seems to be that there is something mysterious about it， and before any research can be done it is necessary to have expensive scientific apparatus and large， elaborately equipped laboratories. Actually， this is not so. （6） It is a simple， organized way of trying to accomplish something you wish to do—so simple that anyone can do research anywhere at any time.First， you select the problem you would like to solve， then you list at least ten reasons why it has not been solved. （7） It takes just as much effort to solve a useless problem as a useful one. （8）After carefully—and I want to emphasize that word “carefully”—selecting the problem and the ten things between you and the solution， you then use the same procedure as in solving a crossword puzzle.（9）In the solution of the remaining obstacles you may need some simple apparatus， but the things you will probably need most are infinite patience and persistence. Few people realize the difficulties of doing any new thing.Maybe one of the reasons people are so easily discouraged is because of their education. During all our years at school we were examined two or three times a year. If we failed once， we were out. （10）If we are going to make progress， we must learn to fail intelligently so that we won't become discouraged at the 99.9 per cent failure. 9.（）A、Make sure the game is worth the candle.B、That is a step in the right direction， but I don't believe it is enough.C、You take the easy obstacles first and by a process of elimination you eventually arrive at the one or two major ones.D、But in selecting the problem， you need to be sure to analyze it carefully to see that it is worth the effort.E、Research isn't a physical thing at all； it's a state of mind.F、By contrast， all research work is 99. 9 per cent failure and， if we succeed once， we are in.

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第7题

I think your sister is old enough to know （） to spend all her money on fancy goods.A、better thanB、thanC、other thanD、rather than

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单选题The author thinks that ______.A packing is actually useless and could be ignoredB people will soon stop using packaging altogetherC enough research has been done into recyclingD it is better to produce new materials than to re-use old ones

题目

更多“单选题The author thinks that ______.A packing is actually useless and could be ignoredB people will soon stop using packaging altogetherC enough research has been done into recyclingD it is better to produce new materials than to re-use old ones”相关问题

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