预制构件制作模具质量验收中,底模平整度的允许误差为()
A.±1mm
B.±2mm
C.±3mm
D.±4mm
参考答案:B
We can't go out ________________ school nights.[ ]
A. at
B. for
C. on
D. in
往复式压缩机连杆大头采用薄壁瓦时,检修时,一般不需要刮研,接触不良时,可稍稍拂刮。