单项选择题
A.Ⅰonly is correct
B.Ⅱ only is correct
C.both Ⅰ and Ⅱ are correct
D.neither Ⅰ or Ⅱ are correct
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 （）
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 （）