单项选择题
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
单项选择题 Before shutting off the fuel supply to stop a medium or high–speed diesel engine, why is it necessary to allow the engine to idle for a few minutes?（）
单项选择题 Clogged diesel engine fuel oil filters can cause（）
单项选择题 If a single cylinder relief valve on a main propulsion diesel engine begins to lift, but it is not possible to secure the engine, which of the following actions should be taken?（）