单项选择题
During bunkering, the request for stoppage of pumping shall be made, as a rule, 5 minutes （）.
A.ago B.before C.ahead D.front
单项选择题 The clutch band of a constant tensioning mooring winch must be set up tight enough to drive the winch drum and should slip only when （）.
单项选择题 The advantages of flash type evaporators, as compared to submerged tube type evaporators, include （）.
单项选择题 The （）is used to burn oil sludge.
