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 （）.
A.excessive loads are placed on the winch B.minimum pull is being exerted by the winch C.automatic operation of the winch is desired D.wire is being retrieved at the maximum rate
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.
单项选择题 Which is the pollution prevention equipment?（）
