第6部分：完形填空

　　阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。

What Is the Coolest Gas in the Universe?

　　What is the coldest air temperature ever recorded on the Earth? Where was this low temperature recorded? The coldest recorded temperature on Earth was -91℃ which -1- in Antarctica in 1983．

　　We encounter an interesting situation when we discuss temperatures in-2-. Temperatures in Earth orbit actually range from about +120℃ to -120℃．The temperature depends upon -3- you are in direct sunlight or shade．Obviously, -l20℃ is colder than our body can safely endure．Thank NASA science for well-designed space -4- that protect astronauts from these temperature extremes．

　　The space temperatures just discussed affect only Our areal of the solar -5-．Obviously，it is hotter closer to the Sun and colder as we travel away from the Sun．Astronomers estimate temperatures at Pluto are about -210℃．How cold is the lowest estimated temperature in the entire universe? Again，it depends upon your -6-．We are taught it is supposedly -7- to have a temperature below absolute zero，which is-273℃，at which atoms do not move．Two scientists，whose names are Cornell and Wieman，have successfully cooled down a gas temperature barely -8- absolute zero．They won a Nobel Prize in Physics in 2001 for their work-not a discovery，in this case．Why is the two scientists' work so important to science?

　　In the l920s，Satyendra Nath Bose was studying an interesting -9- about

　　particles we now call photons．Bose had trouble -l0- other scientists to believe -11- he contacted Albert Einstein．Einstein's calculations helped him theorize -12- behave as Bose thought——but only at very cold temperatures．

　　Scientists have also discovered that -13- atoms can help them make the world's atomic clocks even more accurate．These clocks are so accurate today they would only lose 0ne second -14- six million years! Such accuracy will help us travel in space because distance is velocity times time （d=v×t）．With the long distances involved in space -15- to know time as accurately as possible to get accurate distance．

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