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

You answered correctly because both abrupt steering and strong braking while turning increase the risk of a combination vehicle jack-knifing or skidding on slippery roads. Abrupt steering can cause the trailer to lose stability and swing out, while heavy braking on a curve reduces traction and can lead to a loss of control. Gradual acceleration, on the other hand, is safer in slippery conditions because it helps maintain stability and prevents wheel slip. Understanding these points helps you recognize that sudden or strong maneuvers on slippery surfaces are dangerous for combination vehicles.