The vehicle's speed can be reduced...

Correct answer

With the brakes and the engine.

The vehicle's speed can be reduced by using both the brakes and the engine. Using the brakes is the most common and direct method of reducing speed; it consists of applying braking force directly to the wheels. The engine brake, on the other hand, works by reducing the engine's revolutions, achieved by taking your foot off the accelerator or changing to a lower gear, allowing the engine to help control the vehicle's speed. This braking technique has additional advantages, such as less brake wear and reduced fuel consumption and emissions.