How can you reduce the speed of your vehicle?
A)Only with the braking system.
B)Only with the engine.
C)Both with the braking system and with the engine.Correct
# Explanation
To reduce the speed of a vehicle, you can use **both the braking system and the engine**. The braking system is the most direct and effective method, while the engine (by downshifting) provides complementary braking especially useful on long descents. Both systems working together allow for safer and more efficient speed control.