premise: Here is a young woman standing in the street in front of a department store. hypothesis: Two goldfish are riding bikes in a giant pile of mashed potatoes.
contradiction: A young woman and two goldfish are not the same gender nor number of subjects. Also it is not possible to be standing and riding a bike at the same time. It is also not possible to be in a giant pile of mashed potatoes and in the street in front of a department store at the same time.