premise: A man wearing a white t-shirt and shorts is rock climbing with other people wearing blue hard hats. hypothesis: A man in a black t-shirt and shorts is hiking up a mountain.
contradiction: A man can either wear a black t-shirt or a white t-shirt but not both.|contradiction: A black t-shirt is not a white t-shirt.  If a man is rock climbing he is not hiking up a mountain.|contradiction: white not same as  black.