单项选择题
If the operating element of a thermostatic valve installed in a diesel engine cooling system malfunctions, it may result in （）
A.a low level in the engine expansion tank B.excessively high coolant pressure C.improper temperatures D.malfunctioning of the jacket water heater
单项选择题 Why is the ring belt narrower in diameter than the skirt of a piston designed for a diesel engine?（）
单项选择题 The effective pump stroke of an individual port-and-helix fuel injection pump is determined by the （）
单项选择题 The upper section of a piston is called the （）
