单项选择题
The piston rings if found worn out （） and supplied by shipchandler.
A.must replace B.must to be equipped C.has to be repaired D.have to be renewed
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 （）
单项选择题 The piston moving up and down keeps the crankshaft （）.
