单项选择题
The piston rings are manufactured with a diameter （） the bore of the cylinder.
A.larger than B.smaller than C.equal to D.none of the above
单项选择题 The piston ring grooves for a standard engine are （）
单项选择题 The piston moving up and down keeps the crankshaft （）.
单项选择题 The piston moves up and down, thus causing the rotational movement of the（）
