White smoke exhausting from an operating diesel engine may indicate （）.

A.increasing the volume of intake air
B.shutting off the fuel supply
C.increasing the engine back pressure
D.over-speeding the engine

A.During operation at low speed
B.During operation at rated speed, but low power output
C.During acceleration
D.All of the above

A.compression pressures are below normal
B.lube oil is diluted with fuel oil
C.cranking speed is too low
D.exhaust system is partially restricted