单项选择题
A.open B.uncover C.covered D.closed
Hearing a strong noise, （） at once.A.the engine stopped...
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
（） that everything in the engine crankcase is correct, ...
单项选择题（） that everything in the engine crankcase is correct, start up the crankcase lubricating oil pump.
A.To satisfy B.To be satisfied C.After satisfying D.After being satisfied
Cooling （） the engine metals retain their mechanical pr...
单项选择题Cooling （） the engine metals retain their mechanical properties.
A.forces B.enables C.makes D.is able to
