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

The combination of choices that you selected is correct because both scenarios significantly increase the risk of a combination vehicle jack-knifing or skidding on slippery roads. Abrupt steering can cause the vehicle's rear to swing out, losing traction and control, especially in adverse weather conditions. Meanwhile, applying maximum pressure on the brakes while driving around a bend reduces traction on the wheels, leading to potential skidding.

In German traffic regulations, it is essential to maintain vehicle control, especially in challenging weather conditions. Understanding these risks helps drivers make safer choices to prevent accidents. Gradual acceleration, as mentioned in the third option, is typically a safer approach to maintain traction, hence it was excluded from the correct combination.