Which of the following is a common cause of vehicle skids?

Sudden braking or turning is a common cause of vehicle skids because these abrupt actions can disrupt the vehicle's balance and traction with the road surface. When a driver suddenly brakes, the weight of the vehicle shifts forward, which can lead to the wheels losing grip, especially on slick or uneven surfaces. Similarly, quick turns can cause the tires to lose traction and may result in a skid, particularly if the turn is executed at high speeds or in poor weather conditions. Smooth and gradual maneuvers help maintain control of the vehicle, reducing the risk of skidding.

Other factors like weather conditions certainly contribute to skids by affecting road surface grip, but it's the sudden and sharp inputs from the driver that are the immediate catalysts for loss of control. Constant speed can enhance stability under normal conditions, while proper tire inflation is crucial for effective traction; however, neither of these involve sudden changes in motion that can lead to skidding.