A 4-cycle engine piston usually has three piston rings which consist of:

A 4-cycle engine piston typically has piston rings designed to fulfill specific roles in the engine's operation. The correct answer identifies the common configuration of two rings dedicated to maintaining compression within the combustion chamber and one ring designed for oil control.

The rings responsible for compression are crucial for sealing the combustion chamber, ensuring that the mixture of air and fuel remains contained during the power stroke. This effective sealing prevents the loss of pressure and maximizes the engine's efficiency and power output.

The oil control ring plays an essential role in managing the lubrication on the cylinder walls. It helps to regulate the amount of oil that reaches the combustion area, thereby minimizing oil consumption and preventing excessive oil from burning, which could lead to increased emissions and fouling of spark plugs.

This configuration of two compression rings and one oil control ring is standard in most modern 4-cycle engines, emphasizing the design's focus on both efficient power generation and maintaining the engine's integrity over time.