单项选择题
The piston supporting body is mainly subjected to （） stress.
A.pushing B.centrifugal C.stretch D.compressive
单项选择题 The piston rings if found worn out （） and supplied by shipchandler.
单项选择题 The piston rings are manufactured with a diameter （） the bore of the cylinder.
单项选择题 The piston ring grooves for a standard engine are （）
