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A Canadian researcher has discovered that sound travels 【21】______ air more than one-haft kilometer an hour slower than had been
A Canadian researcher has discovered that sound travels 【21】______ air more than one-haft kilometer an hour slower than had been
admin
2010-06-30
54
问题
A Canadian researcher has discovered that sound travels 【21】______ air more than one-haft 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 microphones. 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 al ways have 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.
【29】
选项
A、resource
B、source
C、origin
D、reason
答案
D
解析
本句意为“他最后找到了产生区别的原因”。A“资源”;旷来源”;C“起源、由来”,均不合题意。只有D项“理由,原因”正确。
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公共英语四级笔试题库公共英语(PETS)分类
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