premise: a skier is throwing up snow as he skis off piste. hypothesis: A snowboarder takes a nap on the course.
contradiction: the two actions are contradictory, to ski is active and to take a nap is to rest.|contradiction: you cannot be a skier and snowboarder simultaneously or ski and nap at the same time.|contradiction: A skier is not a snowboarder. A person cannot be throwing up snow if they're taking a nap.