Which of the following are types of piston rings?

The types of piston rings are primarily categorized into three main functions: compression, oil control (also known as oil scraper), and sometimes, variations in terminology may include ring designs that group them under broader categories.

Compression rings are designed to seal the combustion chamber, preventing the escaping of gases during the combustion process. They play a crucial role in maintaining engine efficiency and power output by ensuring that compression is maximized within the cylinder.

Oil control rings, often referred to as oil scrapers, function to regulate the amount of oil that coats the cylinder walls and reduces the amount that enters the combustion chamber. This helps to prevent excessive oil consumption and minimizes the potential for carbon buildup in the combustion chamber.

In the context of this question, the selection that accurately reflects these functional categories is correct. The terminology used in option C aligns with standard industry practice, as "oil control" and "oil scraper" are often used interchangeably to describe rings that manage oil in the cylinder.

Other choices introduce different terms or variations that do not consistently align with the recognized types of piston rings in the automotive and aeronautical fields, making option C the most widely accepted and accurate representation.