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【简答题】
50Hz 的工频信号的8次谐波分量的频率是 。
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【单选题】What advantage did the 20th century have over the 19th century?
A.
The new invention of the train made traveling possible.
B.
Information could be spread immediately.
C.
People didn’t get as much exercise anymore.
D.
Travelling by boat was still dangerous.
【简答题】原子弹和核反应堆的主要燃料 ,其原子核内有 个质子, 个中子,核外有 个电子。
【简答题】低于国家等级的普通水准测量,称为____,又称五等水准测量。(答案为6个字)
【单选题】What major development in the 19th century led to a great economic boom for the cowboy?
A.
The cow town settlements.
B.
The construction of the railroads.
C.
The pioneer settlements.
D.
The use of modern technology.
【简答题】I don't know what's your opinion about mountains. It was only in the eighth century people in Europe began to that mountains were beautiful. that time, mountains were feared by the people on the p...
【简答题】低于国家等级的普通水准测量，称为______，又称五等水准测量。
【单选题】What made the American families in the 19th century change greatly?
A.
The disadvantage of the single family pattern.
B.
The great increase of the urban population.
C.
The rapid development of industrialization and the arrival of immigrants.
D.
The improved living conditions and the women's entrance into the work force.
【单选题】Not until the early years of the 19th century ___ know what heat is. [ ]
A.
man did
B.
man
C.
didn't man
D.
did man
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