等离子弧是通过机械压缩、热压缩和磁压缩得到的一种高能电弧()
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Colleen Saffrey would most probably agree that______.
A. people should learn to avoid regret
B. regret is no longer a negative emotion
C. though negative, regret is of value to people
D. regret can help people find the problems
The EUs attitude towards the awake system is one of_____.
A. cautious optimism
B. insufficient support
C. sheer confidence
D. great skepticism
在带压不置换焊补中，容器及管道必须连续保持稳定负压，这是动火安全的关键。()
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