The main job of the piston rings is to

Correct answer to question 2 (Auto & Shop Information): seal the combustion chamber and control oil on the cylinder wall

Method

Compression rings keep the burning gases above the piston and the oil ring wipes excess oil back down. Worn rings let combustion pressure escape and oil burn, which is why a tired engine loses power and smokes. The connecting rod is what joins piston to crankshaft.