CO2气体保护焊和钨极氩弧焊产生的变形比焊条电弧焊小。( )
参考答案:错
The time is not far away____modern communications will become widespread in China’s vast countryside.
A.as
B.until
C.before
D.when
螺纹联接和螺旋传动,螺纹零件都承受轴向力。