In which position of the engine brake switch is maximum engine braking achieved?

Answer: C — High

Maximum engine braking is achieved in the high position of the engine brake switch. When the switch is set to high, it engages the engine brake's full capacity, allowing for the greatest level of deceleration by utilizing the engine's compression forces. This setting activates additional components within the engine brake system, leading to more significant resistance against the motion of the vehicle. In contrast, positions like low or medium provide less braking force, which may be suitable for lighter braking situations but would not offer the maximum deceleration that high provides. The off position completely disengages the engine brake, resulting in no assistance in slowing down, which is contrary to what is desired when maximum braking is required.