Corrosion and grooving on the blade of an exhaust driven turbocharger is caused by certain components of residual fuel oilsThese components are vanadium,sodium, and（）

A.The cylinder indicator cocks should be opened
B.The sump lube oil scavenge pump should be secured immediately
C.The explosion relief valves should be manually opened
D.The crankcase should remain unopened until the engine has cooled

A.turbocharger malfunction or failure
B.crankcase exhauster overload
C.overload on the intercooler
D.obstruction in the engine cylinders

A.inspection covers should not be opened until the engine has cooled
B.ventilation system should be continued in operation for one hour for cooling
C.scavenge pump should be immediately secured to prevent loss of lube oil
D.explosion covers should be opened slightly to provide extra ventilation