Peter _____ breakfast at home every day.[ ]
A. having
B. have
C. has
D. is having
答案:C
制冷系统中的防护设备指用来消除混入()中的机械杂质、污物和水分,保护主要设备的正常安全运行。
A.润滑油
B.冷媒
C.系统
D.制冷剂
钻机油泵主轴与传动轴的同轴度允许偏差不大于()。
A.0.5mm
B.0.2mm
C.0.1mm