当前学科:船舶动力装置
  • 题目: 单选
    The pivot pin at the base of a sheath-screw boom davit must be().

      A . inserted each time before the booms are cranked out
      B . periodically removed for inspection and lubricated
      C . replaced at each inspection for certification
      D . in the locked position after the boat is cradled and griped dow

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