From our smartphones to our latest weaponry, the technology that underpins（支撑） modern life would be impossible without rare earth metals．  The importance of rare earths has only grown as emerging markets increase their demand for technologies made with it, as does the renewable energy industry．
The 17 metallic elements are common in the earth-s crust, but the technique used to extract and refine them is labor-intensive, environmentally hazardous and increasingly costly．  Thomas Gradael,  a professor of geology and geophysics at the Yale School of Forestry Environmental Studies, explains that the钰criticality" of rare earths was only recently understood after China, which dominates the world-s supply of the minerals, cut exports by 40% in 2010, citing concerns over how polluting the rare earth industry was．
Along with colleagues at Yale, Gradael decided to investigate the metals used in modern technologies to determine if there were viable（可行的） substitutes．“Twenty or thirty years ago electronics were being made with 11 different elements," explains Gradael．  “Today's computers and smartphones use something like 63 different elements．" Their findings showed that there were no "readily apparent" substitutes for a metal that would not compromise on quality or performance．
However increased mining for these scarce resources can have some nasty side effects for the environment． China, which has intensively mined for rare earths with little regulation, allowing it to dominate the global industry since 1990, has acknowledged the incredible environmental harm caused by the process．  “Excessive rare earth mining has resulted in landslides, clogged rivers, environmental pollution emergencies and even major accidents and disasters, causing great damage to people's safety and health and the ecological environment," read a white paper issued by the Chinese cabinet in June last year．
Recycling metal has been advocated by some as a possible way of managing these precious resources-the European Parliament adopted a law curbing dumping of electric waste in 2012． But Gradael says that for rare earths, recycling will have little impact．
Rare earths are growingly important in that

A．they exist in small numbers

B． they are essential in modern technologies

C．life would be impossible without them

D．new technology markets are emerging

Which one of the following can be used in the blank?

A．It is in China that rare earths are fully understood．

B．Despite the name, rare earth metals are not in fact rare．

C．There is a growing concern over the rare earth industry．

D．Rare earth metals are difficult to collect though important．

Gradael investigated the use of rare earths in modern technologies to        ．

A．prove the important role rare earths play

B．learn the number of different elements used

C．determine whether there are substitutes for rare earths

D．research further the quality or performance of rare earths

Why does the author take China as an example in Para．4?

A．To tell the wide use of rare earth in China．

B．To prove the side effects of rare earth mining．

C．To warn people of the possible damage．

D．To teach other countries a lesson to follow．

The text may probably be followed by the paragraphs about

A．the reasons why recycling works little

B．the ways to manage rare earths

C．the effects brought about by rare earths

D．the attitudes people hold to the law

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