单项选择题
If a gasoline engine turns over freely but will not start，the cause is generally（）.
A.a defective ignition system B.low lube oil level C.weak valve springs D.too heavy a load
单项选择题 Each cylinder in a two stroke cycle engine experiences combustion（）.
单项选择题 Centrifugal pumps have what advantage(s) over reciprocating pumps?（）.
单项选择题 Cargo pump relief valves are piped to the（）.
