1946年，国际计量委员会(CIPM)提出定义为:在真空中，截面积可忽略的两根相距1米的平行而无限长的圆直导线内，通以等量恒定电流，导线间相互作用力在1米长度上为2×10牛时，则每根导线中的电流为1安培，又称绝对安培。该定义经1948年第9届国际计量大会(CGPM)通过沿用至今 。
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Generally speaking,how many methods of delivery are there ? what are they?
A. speaking impromptu
B. speaking extemporaneously
C. reciting from memory
D. reading from a manuscript
E. rehearsing the speech
Reading from a manuscript doesn't need any skill.
A. 对
B. 错
You should concentrate on the words in your speech when you recite from memory.
A. 对
B. 错
There are four steps you can follow when you try to speak impromptu.
A. 对
B. 错
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