单项选择题
An increased differential between the inlet and outlet of a strainer usually indicates the strainer is （）
A.holed B.fouled C.clean D.dry
单项选择题 Trunk type diesel engine pistons are effectively cooled when heat is（）
单项选择题 Maintaining the proper fuel oil temperature will result in （）
单项选择题 Air motion is induced in a four-stroke/cycle diesel engine cylinder to improve air fuel mixing, and is known as（）
