单项选择题
A few spots of turbocharger can be caused by（） ①crash stop of engine ② rapid increased of engine speed
A.①only is correct B.②only is correct C.both ① and ②are correct D.neither ① or ② correct
单项选择题 The function of synchronous compensating machine is to（）
单项选择题 What is head tank in the closed cooling water system used for?（）
单项选择题 According to the principle of four stroke diesel engine, what is the number of its efficient work stroke per revolution?（）
