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Masses of floating ice are so large that they dwarf your ship，making you question whether your ship still can be spotted among such floating mountains.They are so improbable looking that you simply look in wonder.It seems that nothing that large could be natural—and then it strikes you that something so large could only be natural.

Now，people realize that as climate change is raising global temperatures，more icebergs are being born.Antarctica creates far more of them than Greenland，the source of bergs in Arctic waters.Antarctica's are also much larger，sometimes reaching the size of small  countries.Recent  data  show  the  average  atmospheric temperature has increased about 4.5°F

in the western Antarctic Peninsula since the 1940s，making the region，among the fastest warming on earth.This jump has been shown in the recent breaking of major ice shelves along the Antarctic Peninsula.As a result，thousands of new icebergs have broken off，from ice shelves into the Southern Ocean at an accelerated rate.

Even as more icebergs are being created，scientists are learning that they are far from inactive masses of ice.In fact，they strikingly alter their environments biologically，chemically，and physically，making them islands of life in the open sea.Observers at sea have long remarked that they attract seals，and seabirds，and divers have noticed that fish are more numerous near them than in the surrounding sea.Now scientists are learning just what the attraction is all about.

Depending on their size，location，and the season，icebergs can be nurturers (培养者) or destroyers.During their existence—typically years from breaking off from an Antarctic or Greenlandic glacier to their gradual melting as they float into lower altitudes，they support animals on，around，even inside their splendid ice castle.They fertilize the ocean with nutrients，increasing sea creature production.Grounded bergs can shelter areas of the seafloor，protecting  bottom－living  creatures  from so large that they dwarffree－floating  icebergs.However，large bergs can also trap sea ice，preventing its annual breakup and thus stopping phytoplankton (浮游植物) from getting life—giving sunlight，breaking the food chain at its first link.

Icebergs will continue to astonish and attract visitors to the polar regions.But now these frozen large masses are taking on a new dimension of wonder as we uncover their vital role in the environment of polar seas.No longer can we look at icebergs as mere passive white mountains floating in the sea.They are active agents of change，each one is an icy oasis with awake of life as it floats on its unstoppable oceanic journey to melting.

解析

【语篇解读】　本文为说明文，介绍了随着全球气温不断上升，冰山数量不断增多。冰山的增多从生物、化学、物理等多个方面改变着环境，对海洋既有利也有弊。

46．Why does the author mention “dwarf__your__ship” in the first paragraph?

 A．To explain how natural icebergs are.

 B．To show how powerful icebergs are.

 C.To describe icebergs as floating ships.   zk.yggk.net

 D．To tell the unbelievable size of icebergs.

 答案　D　[推理判断题。根据第一段第一句Masses of floating ice are so large that they dwarf your ship，making you question...such floating mountains.可知作者是想表达冰山难以置信得大。]

47．What can we learn from the passage?

 A．The temperature in Arctic is rising faster than that in Antarctica.

 B．The ocean food chain breaks due to the melting of icebergs.

 C．Floating icebergs help shelter bottom－living ocean creatures.

 D．Global warming has kept bringing icebergs into being.

 答案　D　[细节理解题。根据第二段第一句可知D项正确。根据第二段第四句．..the average atmospheric temperature...among the fastest warming on earth.可知A项错误；根据第四段第四句Grounded bergs can...from free floating icebergs可知C项错误；根据第四段第五句However，large bergs...at its first link.可知B项不正确。]

48．From the passage we can conclude that icebergs can ________．

 A．preserve ocean creatures

 B．carry ocean nutrients away

 C．create a warm polar environment

 D．keep sea animals away from polar seas

 答案　A　[细节理解题。根据第四段第三句They fertilize the ocean with nutrients，increasing sea creature production.可知A项正确。]

49．What is the author's attitude toward icebergs?

 A．Cautious.   B．Objective.

 C．Doubtful.   D．Disapproving.

 答案　B　[推理判断题。通读全文可知作者只是在客观描述事实，并未表达任何个人观点，因此B项正确。cautious意为“谨慎的”；doubtful意为“怀疑的”；disapproving意为“不赞成的”。]