题目内容：
请根据短文的内容，回答题。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 _______ （51）in Antarctica（南极洲） in 1983．
We encounter an interesting situation when we discuss temperatures in _______（52）.Temperatures in Earth orbit（轨道） actually range from about +120℃ to -120℃．The temperature depends upon _______ （53）you are in direct sunlight or shade． Obviously, -120℃is colder than our body can _______ （54）endure．
The space temperatures just discussed affect only our area of the solar _______ （55）．Obviously，it is hotter closer to the Sun and colder as we travel _______（56）from the Sun． Scientists estimate temperatures at Pluto are about -210℃．How cold is the lowest estimated temperature in the entire universe? Again, it depends upon your _______ （57）． We are taught it is supposedly _______ （58）to have a temperature below absolute zero, which is -273℃，at which atoms do not move. Two scientists, Cornell and Wieman， have successfully_______ （59） down a gas to a temperature barely above 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 1920s,Satyendra Nath Bose was studying an interesting _______（60） about special light particles （颗粒） we now call photons （光子）．Bose had trouble _______ （61）other scientists to believe his theory， so he contacted Albert Einstein．Einstein's calculations helped him theorize that atoms_______（62）behave as Bose thought—but only at very cold temperatures.
Scientists have also discovered that ultra-cold （超冷） atoms can help them make the world's atomic clocks even _______ （63） accurate．These clocks are so accurate today they would only lose one second _______ （64）six million years! Such accuracy will help us travel in space because distance is velocity times time(d=vt)．With the long distances involved in space_______（65），we need to know time as accurately as possible to get accurate distance．
________ A．operated
B．opened
C．offered
D．occurred
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