Cylinder linings constructed as an integral part of the block, are characterized by which of the following disadvantages?（）

A.The diesel oil must never be allowed to mix with the heavy fuel
B.The temperature of the fuel from the pre–heater should be gradually reduced after switching over the three–way valve
C.The heating steam to the pre-heater should be secured as soon as the diesel fuel passes through the three-way valve
D.The heating steam must be secured before the diesel oil passes through the three-way valve

A.To prevent internal damage form local overheating
B.To ensure the fuel nozzles are flushed clean
C.To clear the smoke stack
D.To let the waste heat boiler reduce its rate of steam generation

A.loss of power
B.misfiring
C.low fuel oil pressure
D.All of the above