(来学网)用机器调拌石膏,在真空状态下搅拌,以多久为佳?()
  • A.
    (来学网)15~20s
  • B.
    (来学网)20~30s
  • C.
    (来学网)30~45s
  • D.
    (来学网)1min
  • E.
    (来学网)2min