Questions 56 to 60 are based on the following passage．
　　Arctic Ocean ice may hold trillions of small pieces of plastic and other synthetic trash，and they are being released into the world’s oceans as global warming melts the polar cap，researchers say,Though the finding is surprising and worrying，the possible harm to marine life is so far unknown，the authors concluded．called micro plastics，the pollutants come mostly from debris that has broken apart，as well as from cosmetics and fibers released from washing clothes，according to the Study,which was published in the iournA. Earth’s Future and first reported by Science magazine．
　　At current melting trends．more than l trillion pieces 5 millimeters or smaller could wind up in the oceans during the coming decade．the authors estimate．The concentration of plastic debris is 1，000 times greater than that floating in the so．called Great Pacific Garbage Patch．The researchers based their findings on core samples of ice taken during polar expeditions in 2005 and 2010．
　　Rayon was the most colninon synthetic material discovered—54％．Though rayon is not a plastic(it’s made from wood),the authors included it“because it is a manmade semi．synthetic that makes up a significant proportion of synthetic microparticles found in the marine environment．”Rayon is used in cigarette filters，clothing and personal hygiene products．Polyester(聚酯)was the next most common pollutant found in the ice(21％)，followed by nylon(16％)，polypropylene(聚丙烯)(3％)and polystyrene，acrylic and polyethylene (2％each)．
　　The authors cA.led the ice trap“a major historic globA. sink of man．made particulates．”and said their findings“go some way to help clarify one of the most puzzling aspects of current understanding on the quantities of plastic debris reported in the oceans．”As Science points out，288 million tons of plastics were produced in 2012．
　　Micro plastics garbage has aso been found on the shores of southernmost Chile，so the authors said it’s time to investigate the planet’s other polar region．“WHile multiyear sea ice makes up a smaller proportion of aunual sea ice cover in the Southem Ocean．and perenniA. sea ice cover around Antarctica is following different trends,our finding indicate the importance of sampling ice from the Antarctic to see if it too contains micro plastics，”they write．

56．According to the passage．what are mainly called“micro plastics”?
A.The pollutants come mostly from debris．
B.The pollutants come mostly from fibers．
C.The pollutants come mostly from cosmetics．
D.The pollutants come mostly from daily supplies．
57．What does the phrase“wind uP”mean in Para．2?
A.putan endto
B.screwup
C.sweep across
D.roll up
58．Why does the author include“rayon”in．though it is not a plastic?
A.Because it is a significant manmade semi．synthetic discovered in the ocean．
B.Because it is a major natural semi．synthetic appearing in the marine．
C.Because it is a minor manmade synthetic dug out in the marine．
D.Because it is a significant natural synthetic explored in the marine．
59．What can we infer from the ice trap“a major historic global sink of mail-made particulates”?
A.The historic sink should be attributed to man-made particulates．
B.People on a worldwide scA.e have reaped what they had sown．
C.The ice trap is of major historic meaning on the globA. context．
D.The major historic globA. sink is derived from the ice melting．
60．What’s the best title of this passage?
A.Rayon was the most common synthetic in the ocean．
B.It’s time to research the planet’s other polar region．
C.Trillions of plastic pieces found in the Arctic ice．
D.Trillions of plastic pieces will wind up in the ocean．

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