单项选择题
A.fouled tubes in shell and tube condenser
B.too little or too warm condenser water
C.air or non-condensable gas in system
D.overcharge of refrigerant
单项选择题 （）, or drum is used for hauling in or letting out the wires or ropes which will fasten the ship to the shore.
单项选择题 （） unit is mounted so as to raise and lower the cable from the spurling pipe, which is at the top and center of the chain or cable locker.
单项选择题 Topping wires fix the height of the derricks and （） to the deck may be used to prevent fore and aft movement.