Which condition can significantly increase the risk of skidding while riding?

The condition that significantly increases the risk of skidding while riding is wet or slippery road surfaces. When the road is wet or covered with substances like oil, mud, or leaves, the friction between the tires and the road decreases. This reduced traction can cause the motorcycle to lose grip, making it easier to skid, especially during turns or when braking.

In addition to lowering traction, wet or slippery conditions can lead to hydroplaning, where tires ride on a film of water instead of making contact with the road. This can greatly impair a rider's ability to control the motorcycle, increasing the likelihood of losing balance and resulting in a fall.

Other conditions like braking too hard or riding downhill can also lead to instability, but the immediate impact of wet surfaces on traction makes them particularly dangerous. Riding on dry road surfaces normally provides better grip, while a downhill slope may just require more control and technique rather than an inherent risk of skidding.