单项选择题
A.Combustion gases flow through the tubes B.Flames impinge on the tubes C.Combustion occurs in the tubes D.Water flows through the tubes
A.slight acidity B.slight alkalinity C.excessive alkalinity D.excessive acidity
A.cold corrosion of the nozzles B.fuel viscosity for better atomization C.carbon accumulation on the nozzles D.fuel detonation in the cylinders