单项选择题
If a cam-controlled engine has a normal injection pressure at rated speed,the injection pressure will be（）at slow speed.
A.a little lower B.a little higher C.too low D.exactly the same
单项选择题 The main purpose of changing main engine to electronic controlled is not to（）
单项选择题 To meet the market requirements, a marine diesel engine should not be of（）
单项选择题 The common rail engines show great advantages in combustion especially（）.
