单选题Exhaust valve grooving and corrosion is caused by certain components of residual fuel oilThese components are sodium, sulfur, and （）.AvanadiumBcarbonCcopperDash
单选题
Exhaust valve grooving and corrosion is caused by certain components of residual fuel oilThese components are sodium, sulfur, and （）.
A
vanadium
B
carbon
C
copper
D
ash
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