2. 外语
  3. A Canadian researcher has discovered that sound travels 【21】______ air more than one-half kilometer an hour slower than had b

A Canadian researcher has discovered that sound travels 【21】______ air more than one-half kilometer an hour slower than had b

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问题      A Canadian researcher has discovered that sound travels  【21】______   air more than one-half kilometer an hour slower than had been believed. The discovery has surprised many engineers and scientists who learned they had been  【22】______   the wrong speed of sound for many years.
      The speed of sound in air had been【23】______ to be three-hundred-thirty-one-point-two-nine meters a second. But Doctor George Wong found,  【24】______   accident, that the speed of sound is only three-hundred-thirty-one-point-one-three meters a second. That is a difference of about sixteen centimeters a second.
      Doctor Wong is a member of the National Research Council of Canada. He was studying ways to    【25】______   exactly the sound created by microph ones. One of his experiments  【26】______   a number he could use to find the speed of sound. He was  【27】______   to learn that the speed of sound was slower than scientists had thought.
      To explain the difference, Doctor Wong spent eighteen months  【28】______   past test research on the speed of sound. He finally found the  【29】______   of the difference. It was a mathematics mistake  【30】______   in Nineteen-Forty-Two by physicist H-C Hardy.
      Doctor Wong’s  【31】______   does not mean a big change for the science of sound. This is    【32】______   Doctor Hardy and Doctor Wong measured the speed of sound for what is called" standard air".
    Standard air exists only  【33】______   thought. It is a way for scientists to agree  【34】______   the same speed of sound.  【35】______   the air around us, standard air always has a temperature of zero degrees Celsius and the same atmospheric pressure  【36】______   the air at sea level. Standard air always has same amounts of nitrogen, oxygen, carbon dioxide and  【37】______   gases. And in standard air, the speed of sound does not change.
    The change in the new speed of sound is  【38】______   small to affect the work of most sound scientists  and engineers. But scientists say Doctor Wong’s discovery may  【39】______   improve instruments  【40】______   use the speed of sound to measure very short distances.
【30】
选项 A、did
B、committed
C、had
D、made
答案D
解析 make a mistake犯错误，是固定搭配。
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