单项选择题 Exhaust valve grooving and corrosion is caused by certain components of residual fuel oilThese components are sodium, sulfur, and （）.

单项选择题 Which of the following problems may occur if the opening pressure of a fuel injection nozzle is greater than specified by the engine manufacturer?（）

单项选择题 The required amount in the change of speed necessary before a governor will make a corrective movement is known as （）.