单项选择题
Hearing a strong noise, （） at once.
A.the engine stopped B.the engine was stopped C.he stopped the engine D.he had stopped the engine
单项选择题 （） that everything in the engine crankcase is correct, start up the crankcase lubricating oil pump.
单项选择题 Cooling （） the engine metals retain their mechanical properties.
单项选择题 The data to be recorded on this sheet （） the performance of the engine.
