What is the process called in a two-stroke diesel engine by which fresh air is forced into the cylinder to sweep out combustion products?

Why C is correct

Because a two-stroke engine has no separate intake or exhaust stroke, fresh air must be forced in under pressure to displace combustion products; this process is called scavenging. Supercharging and turbocharging are methods of raising intake air density, and aftercooling removes heat from compressed charge air — all are related but distinct terms.