What does 'engine retarding' refer to in diesel engines?

Engine retarding in diesel engines refers to the process of slowly reducing engine speed without relying on the vehicle's braking system. This is typically accomplished through techniques such as engine braking, which utilizes the engine's compression to create a retarding force that slows down the vehicle. This method is particularly advantageous for maintaining control and reducing wear on the brakes during long descents or when coming to a stop, making it safer and more efficient in numerous driving situations.

Choosing this option reflects an understanding of how diesel engines can utilize their inherent mechanical properties to aid in deceleration, thereby promoting more sustainable driving practices and enhancing engine longevity. The other options do not accurately define engine retarding; for instance, accelerating the engine or increasing output power are unrelated to the concept of reducing speed.