Excessive vibration in an operating diesel generator may be caused by （）

A.check the air filter for obstruction
B.check for an exhaust leak
C.check the exhaust temperature
D.secure the engine

A.over-speeding of the engine
B.failure of the engine to shut down
C.no effect of engine mounting bolts
D.high exhaust temperatures

A.low lube oil temperature
B.low starting air temperature
C.air bubbles in the fuel oil system
D.water in the starting air system