When is there a particularly high risk of a combination vehicle jack-knifing or skidding on a slippery road?

The correct combination of choices emphasizes critical driving techniques that can lead to a jack-knife or skidding scenario on slippery roads.

Firstly, steering abruptly can cause a sudden shift in weight distribution, making it difficult to maintain control of a combination vehicle, leading to a potential skidding or jack-knifing effect.

Secondly, applying maximum pressure on the brake while turning can cause the wheels to lock up, greatly reducing traction and control, especially on wet or icy surfaces. This is particularly dangerous as it can lead to a loss of stability in the vehicle.

Gradual acceleration, while safer, is not a factor that contributes to skidding or jack-knife situations, hence it is not included in the correct answer.

Understanding these risks is crucial for safe driving, particularly with combination vehicles, as maintaining control and stability on slippery roads can prevent accidents and ensure safety for all road users.