premise: A crowd of people in winter garb gather in the street against a backdrop of bare trees and snow. hypothesis: Sasquatch is riding a bike on the street.
contradiction: It cannot be both Sasquatch and a crowd of people at once, and Sasquatch do not ride bikes (or maybe they would if they were real).|contradiction: The people gather in the street is different than Sasquatch is riding a bike.|contradiction: A crowd of people cannot be Sasquatch.  Riding a bike doesn't match the actions of gathering in the street.