单项选择题
A.be jammed B.be opened C.be seated D.be broken
The most common cause of lowering the crankcase lube oi...
单项选择题The most common cause of lowering the crankcase lube oil flash point is （）.
A.more water contents B.contamination with fuel oil C.higher temperature D.sufficient cooling of oil mist
The mechanical efficiency of an engine （） because losse...
单项选择题The mechanical efficiency of an engine （） because losses occur in the form of friction.
A.is always less than 100% B.is always more than 100% C.is always equal to 90% D.is always less than 90%
The marine diesel engine is a type of diesel engine use...
单项选择题The marine diesel engine is a type of diesel engine used on ships The （） of its operation is not very difficult to understand.
A.principle B.principal C.cause D.case
