雅思阅读模拟试题学术类 关于这个问题下面小编就来为各个考生解答下。
雅思阅读模拟试题学术类
D The possibility of losing helium forever poses the threat of a real crisis because
its unique qualities are extraordinarily difficult, if not impossible to duplicate . Helium is even cheerfully
derided as a “loner” element since it does not adhere to other molecules like its cousin,
hydrogen. According to Dr. Lee Sobotka, helium is the “most noble of gases, meaning
it’s very stable and non-reactive for the most part … it has a closed electronic 12
configuration, a very tightly bound atom. It is this coveting of its own electrons that
prevents combination with other elements’. Another important attribute is helium’s
unique boiling point, which is lower than that for any other element. The worsening
global shortage could render millions of dollars of high-value, life-saving equipment
totally useless. The dwindling supplies have already resulted in the postponement of
research and development projects in physics laboratories and manufacturing plants
around the world. There is an enormous supply and demand imbalance partly brought
about by the expansion of high-tech manufacturing in Asia.
E The source of the problem is the Helium Privatisation Act , an American
law passed in 1996 that requires the U.S. National Helium Reserve to liquidate its helium
assets by 2015 regardless of the market price. Although intended to settle the original
cost of the reserve by a U.S. Congress ignorant of its ramifications, the result of this fire
sale is that global helium prices are so artificially deflated that few can be bothered
recycling the substance or using it judiciously. Deflated values also mean that natural
gas extractors see no reason to capture helium. Much is lost in the process of extraction.
As Sobotka notes: "he government had the good vision to store helium, and the
question now is: Will the corporations have the vision to capture it when extracting
natural gas, and consumers the wisdom to recycle? This takes long-term vision because
present market forces are not sufficient to compel prudent practice”. For Nobel-prize
laureate Robert Richardson, the U.S. government must be prevailed upon to repeal its
privatisation policy as the country supplies over 80 per cent of global helium, mostly from
the National Helium Reserve. For Richardson, a twenty- to fifty-fold increase in prices
would provide incentives to recycle.
F A number of steps need to be taken in order to avert a costly predicament in the
coming decades. Firstly, all existing supplies of helium ought to be conserved and
released only by permit, with medical uses receiving precedence over other commercial
or recreational demands. Secondly, conservation should be obligatory and enforced by a
regulatory agency. At the moment some users, such as hospitals, tend to recycle
diligently while others, such as NASA, squander massive amounts of helium. Lastly,
research into alternatives to helium must begin in earnest.
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